Plastics are widely used as packaging materials, insulators, components in various machines and devices, and as coating agents. Unfortunately, their widespread use has led to increasing environmental concerns as they are now frequently found in the environment.  Recycling offers a potential solution—but not all chemical recycling methods are equally environmentally friendly. The following provides an overview of chemical processes used to recover value from plastic waste.

Type and Composition of Plastic Waste

The choice of recycling method depends on the physical characteristics of the material and the degree of contamination or  interaction with other substances. Plastics fall into three main categories: thermoplastics, thermosets, and elastomers. Thermoplastics, such as PVC, polyethylene, and polypropylene, soften when heated and can be reshaped and reused once cooled.

These materials can only be recycled by chemically breaking down the molecular bonds in their polymer chains. This process known as solvolysis. Elastomers, which behave like rubber, also decompose at high temperatures. However, they can still be recycled in shredded form, for example, as filler in bitumen applications.

The degree of mixing significantly affects the recycling process. Homogeneous plastic waste is easiest to recycle. When different types of plastics are mixed, combined with other materials, or contaminated, extensive sorting and separation steps are often necessary—especially in the case of collected packaging waste, composites, and coated components. Surface coatings, commonly used to enhance the performance of plastic parts, often interfere with recycling and must be removed in advance.

Types of Recovery Processes

There are three main categories of recovery for plastics within sustainable chemical practices: mechanical recycling, chemical (feedstock) recycling, and energy recovery.

• Mechanical recycling preserves the base material. The plastic is cleaned and reprocessed—using dry, wet, or solvent-based techniques—so that it can be reused. These methods are primarily physical and mechanical.
• Chemical recycling (also called feedstock recycling) uses chemical reactions to break down plastics into raw materials, which can then be used to make new products.
• Energy recovery is not considered a recycling method in the strict sense of chemistry. In this process, plastic waste is incinerated to generate energy.

Chemical Recycling Methods

The most common chemical recycling methods are liquefaction (oil recovery), solvolysis, gasification, and pyrolysis. These often require pre-treatment steps to remove contaminants, such as separating multi-layer materials (e.g., beverage cartons, coated films) or stripping surface coatings. Eco-friendly paint stripping agents are available for these tasks.

Liquefaction (Oil Recovery)

In this process, plastics are converted into oily substances through thermal or catalytic reactions, which requires well-sorted plastic waste. The reaction typically occurs in stirred tank reactors at temperatures up to 750°F (400°C). As the plastic liquefies, gaseous by-products and wax-like residues are separated from the resulting oil.

After purification and distillation, the recovered oil can be used as diesel fuel or as a chemical feedstock.

Solvolysis

Solvolysis breaks down the polymer chains in plastics using special solvents. The reaction may be aided by elevated temperatures and is primarily used for recycling thermosets. It yields the original building blocks of the plastic, which are then separated from the solvent.

The solvents are usually reused in a closed-loop system. Depending on the input material, valuable raw components can be recovered from the decomposed polymers.

Gasification

Gasification is conducted at temperatures of up to 2,900°F (1,600°C) and pressures up to 2,175 psi (150 bar) with limited oxygen supply. This oxygen does not support combustion but facilitates the reaction between carbon and oxygen. The process produces a synthetic gas (syngas) composed of carbon monoxide and hydrogen. Before further use, impurities must be removed. Syngas serves as a raw material for a wide range of chemical products, including GTL (gas-to-liquid) oil, which is used in surface treatment applications.

Pyrolysis

Pyrolysis involves the thermal decomposition of plastic waste in the absence of oxygen at temperatures between 300–1,300°F (150–700°C). One of the oldest known pyrolysis methods is the production of charcoal in kilns. Modern pyrolysis of plastics yields solid, liquid, and gaseous products, which can be processed into valuable chemical precursors.

Comparing Recycling Methods

Chemical plastic recycling requires a high amount of energy as well as extensive pre- and post-treatment steps involving additional auxiliary substances. For this reason, material recycling—which reuses materials without chemical changes—is given priority. When this is not feasible, energy recovery is often the more sustainable option. Under certain conditions, however, chemical recycling methods can still be advantageous. They allow harmful substances to be removed from the material cycle and can supply the chemical industry with valuable raw materials.

This is especially true when larger quantities of homogeneous plastic waste from one or similarly composed materials are available. Research is actively working to improve plastic recycling methods, gradually making this form of plastic recovery more prominent in the future.

Regulatory Considerations

This is particularly true when large quantities of homogeneous plastic waste are available from a single or similar source. In the United States, recycling operations must comply with EPA regulations under the Resource Conservation and Recovery Act (RCRA), which governs how facilities manage hazardous and non-hazardous solid waste. Ongoing research is actively improving chemical recycling methods, making them an increasingly viable part of future waste management strategies.

Der Beitrag Plastic Recycling in Chemistry erschien zuerst auf Kluthe Magazine.

In chemistry, fractionation refers to the process of separating mixtures into their individual components. This is achieved using a variety of specialized chemical separation techniques. The term “fractionation” is typically used when mixtures consist of more than two substances that need to be isolated individually or in groups. Here you will find an overview of the most important methods and their areas of application.

Natural Phenomena Commonly Used in Fractionation

Chemistry often utilizes physical methods to separate mixtures. These methods harness natural phenomena such as:

• Changing states of matter at different temperatures (e.g., distillation)
• Differing solubilities of substances (e.g., extraction, precipitation, absorption)
• The natural tendency toward concentration equilibrium (e.g., diffusion, osmosis)
• Selective accumulation of substances on the surface of solids (adsorption)
• Varied permeability of particles or molecules through porous solids (e.g., filtration, ultrafiltration)

Typically, these phenomena lead to equilibrium states where differences are balanced. In chemical fractionation, the intentional adjustment of process parameters such as concentration, temperature, pressure, shifts the equilibrium toward the desired outcome. Mixtures then form distinct phases with substances accumulating differently between each phase or concentrating at the interfaces. Phases may differ by state of matter (solid, liquid, gas) or by immiscibility (such as oil and water). They often separate spontaneously: gases escape from liquids and can be collected, solids settle as sediment, and immiscible liquids form distinct layers. If needed, fractionation is completed using filters, separators, or centrifuges.

Conducting Fractionation

Fractionation in chemistry typically involves sequentially applying different separation methods. For example, solids may first be filtered from a liquid mixture, followed by precipitating dissolved salts, filtering them out, and finally separating the remaining liquid mixture into its components through distillation processes. Each step produces two new fractions, either final products or further processed materials. Examples include:

• Solvent extraction of plant oils from biomass
• Fractional distillation of crude oil or solvent mixtures
• Adsorption of organic pollutants onto activated carbon for wastewater treatment
• Adsorption of water vapor onto silica gel for air drying
• Reverse osmosis for seawater desalination

How Solvent Extraction Recovers Plant Oils from Biomass?

When extracting plant oils from biomass, oil-rich plant parts are mixed with petroleum ether or alcohol. The oils dissolve in the solvent. After the solids are filtered out, the solvent-oil mixture is distilled, resulting in pure oil. Small amounts of oil evaporate with the solvent; this vapor mixture condenses in a cooler and can be reused. Extraction, which involves selectively dissolving components, is frequently used in chemical fractionation. Liquid mixtures are combined with solvents that dissolve the target substances but remain immiscible with other components. This process creates two separate liquid phases, allowing the separation of the solvent and the extracted material.

Fractional Distillation of Crude Oil or Solvent Mixtures

In chemistry, solvent mixtures containing more than two substances are often produced. Such mixtures also occur in surface technology, for example in industrial parts cleaning — more specifically, in solvent-based parts cleaning. Fractional distillation commonly separates these solvents, exploiting differences in vapor pressures. Lower-boiling substances concentrate more in vapor than in liquid phases. As a liquid mixture evaporates, its boiling temperature gradually rises, introducing heavier-boiling substances into the vapor. By periodically collecting and condensing the vapors separately, different fractions containing fewer components from the original mixture are obtained.

Technical Implementation of Fractional Distillation

Fractional distillation is typically performed in distillation columns—tall, vertical steel towers with evaporators at the bottom and condensers at the top. Columns usually contain internal packing materials. As vapor rises, some condensate trickles downward. Constant mass transfer between vapor and liquid phases occurs. Vapor accumulates lighter-boiling components, while heavier substances concentrate in the liquid. Individual fractions are collected at various heights along the column from the liquid phase.

Adsorption of Organic Pollutants onto Activated Carbon for Wastewater Treatment

Activated carbon has the property of retaining organic substances on its surface. This is utilized, for example, in wastewater treatment in chemistry. Activated carbon typically exists as granules, maximizing surface area and adsorption capacity. Water percolates through or is mixed with activated carbon before filtering. Once carbon capacity is exhausted, it can be regenerated with steam, allowing the newly separated solvents to be recovered.

Adsorption of Water Vapor onto Silica Gel for Air Drying

Fractionation also includes air drying by adsorption of moisture onto silica gel or other drying agents. These materials have a high capacity for absorbing water vapor, preventing condensation and moisture-related damage during temperature fluctuations. Small packets of drying agents, such as silica gel, are commonly included with leather goods and metal products during transport to prevent corrosion.

Reverse Osmosis for Seawater Desalination

Membrane-based methods are also frequently used in fractionation. Reverse osmosis for seawater desalination is a prominent example. Osmosis naturally balances concentration differences, causing ripe cherries to burst after rain, for instance. When a concentrated solution (e.g., juice) and water are separated by a semi-permeable membrane allowing only water molecules to pass through, the water moves into the solution, diluting it and increasing internal pressure. When equilibrium is reached, the process stops. In reverse osmosis, applying pressure greater than the equilibrium pressure to the concentrated side forces water through the membrane, enabling the collection of purified water.

Der Beitrag What Does Fractionation Mean in Chemistry? erschien zuerst auf Kluthe Magazine.

A Brief Insight into Electrochemistry

Join us for a short excursion into electrochemistry to better understand the fundamentals that make this process so important in surface technology.

Energy Source

Electrochemistry typically uses direct current sources for anodic oxidation. These are characterized by a positive and a negative terminal. At the negative terminal, an excess of negatively charged electrons is present. Nature tends to equalize this charge difference (also known as electrical voltage or potential difference). Humans have learned to route this equalization through lamps, motors, or heating elements to obtain light, mechanical energy, or heat. Nature has also made it possible to use charge equalization in surface technology: through electrochemical reactions.

Electrodes

Electrically conductive connections between the poles of the DC source and two spatially separated metal objects turn these objects into electrodes. The electrode connected to the negative pole is called the cathode, while the one connected to the positive pole is the anode. In anodic oxidation, the anode is the workpiece that is to receive an oxide layer. To build this layer, an electrolyte is required that surrounds the anode and at least wets the cathode.

Electrolyte

The electrolyte for anodizing consists of bases (alkalis), acids, or salts dissolved in water. These substances consist of electrically positive and negative ions. In water, the ions are separated and freely mobile. At first glance, it seems as if the electrolyte could conduct electricity. On closer inspection, however, the ions migrate to the electrode with the opposite electrical charge, where they accept or release electrons. In doing so, the ions equalize their own charge and undergo chemical transformation.

Chemical Reactions

In chemistry, reactions in which electrons are accepted are called reductions. These reactions occur at the cathode, where there is an excess of electrons. During anodizing, hydrogen gas is typically formed at this electrode.

At the anode, where electrons are lacking, ions release electrons. This  process is known as oxidation. In anodizing, oxygen acts as the electron acceptor and bonds with the electrode material to form a metal oxide.

What Exactly Is Anodizing? Process Sequence of Anodizing

Pretreatment as a Prerequisite for Defect-Free Layer Formation

A uniform oxide layer can only form on metallically clean surfaces. Thorough surface pretreatment is therefore essential. Surface technology provides mechanical and chemical methods that remove all types of contamination from materials.

Mechanical surface treatments remove stubborn contaminants and corrosion products. They also create a defined surface structure—such as glossy or matte—and can eliminate scratches or defects. Mechanical pretreatment typically involves brushing, blasting, grinding, or polishing.

Chemical pretreatment primarily removes contamination from previous process steps, such as oils and greases used as corrosion protection or cooling and forming lubricants from manufacturing. Common steps include alkaline degreasing and pickling in acidic or alkaline baths to remove remaining contaminants and natural oxide films.

Sequence of Anodizing

Individual workpieces are mounted on racks and immersed in the electrolyte bath. Alternatively, sheet metal wound into coils can be drawn through the bath and rewound after anodizing. A conductive connection to the positive pole of the DC source ensures that the workpiece becomes the anode. The container material often serves as the cathode; if that is not possible, cathodes are mounted on the side walls of the tank and connected to the negative pole.

Once the power source is switched on, the ions begin to migrate. Initially, a  thin, electrically insulating metal oxide layer  forms on the workpiece or semi-finished product. Because the anode continues to attract negative ions, these ions accumulate in front of the layer. The voltage rises until it reaches a value that allows the ions to penetrate the layer and reach the base metal to form new metal oxide. This process often produces visible sparks. Oxidation continues at the base metal, forming a porous layer with countless microscopic channels. The structure of the oxide layer can be varied widely  by adjusting the electrolyte composition, current intensity, and temperature.

Post-Treatment to Seal Pores and Add Color

The porous structure of the fresh metal oxide layer is ideal for absorbing dyes. However, if you choose to dye the freshly formed metal oxide layer, the pores must be sealed. This step is usually performed in a hot-water bath. At 208.6 °F (97 °C), the metal oxide reacts with water (hydration). This increases the volume of the layer and compresses the pores. This densification process is known as sealing. As an alternative, surface technology also offers pore filling using waxes.

Applications of Anodizing

Anodizing is well suited for producing corrosion- and wear-resistant oxide layers on light metals. This is primarily due to the properties of the oxides. The process is primarily used for aluminum, titanium, and magnesium. Attempting to anodize stainless steel would fail because its corrosion protection is provided by a very thin oxide film formed by chromium in the alloy reacting with oxygen in the air.

Anodizing Aluminum

Anodizing aluminum is the most widespread and best-studied variant of anodizing. It has acquired its own name: *Eloxal*. Aluminum is used in aerospace, automotive engineering, machinery, equipment manufacturing, construction, and architecture.

Anodizing Titanium

Titanium is an ideal material for aerospace and aviation due to its low density, high mechanical strength, and excellent heat resistance. These properties, combined with outstanding chemical resistance, make anodized titanium valuable for the chemical industry and medical technology.

Anodizing Magnesium

Because magnesium is extremely lightweight yet strong, it is gaining interest in the automotive and equipment manufacturing sectors. However, anodizing magnesium is challenging due to its high reactivity. It requires special approaches both in preparation and during anodic oxidation.

Der Beitrag Surface Treatment by Anodizing erschien zuerst auf Kluthe Magazine.

Work hardening occurs when metallic materials are deformed below their recrystallization temperature. Discover how mechanical properties of metals change during forming processes, which industries benefit from increased material strength, and  the additional hardening methods  used in  various manufacturing processes.

Cold Forming

Cold forming is ideal for mass production due to its ability to achieve high material throughput in a short amount of time. Additional advantages include material integrity, efficient material utilization, and relatively low energy consumption. Metals can be shaped into almost any form using intense mechanical forces. These new contours are created with tools that shape the material according to design specifications.

Despite the high processing speeds, pressures, and temperature increases used in the process, forming lubricants ensure that tools maintain a cost-effective lifespan. Kluthe offers a wide range of friction-reducing products, including Hakuform, Hakuforge, and carrier coatings like Decorrdal zinc phosphating, which are specifically adapted to different manufacturing conditions.

Work Hardening

A key side effect of cold forming is work hardening, which enhances the mechanical properties of manufactured components, allowing them to withstand high operational loads. In most manufacturing processes, increasing material strength is a desired outcome, especially in cold rolling, tube drawing, wire drawing, and other bulk cold forming techniques.

The benefits of work hardening can be seen in everyday American products, from the stronger aluminum used in MacBook laptop bodies, to the durable stainless steel in kitchen appliances like KitchenAid mixers, and even the paperclips on your desk. However, in some cases, increased strength can hinder further processing. When needed, the material can be annealed (recrystallized) to restore its original mechanical properties. This step is essential when multiple forming stages are required to achieve the final shape, such as in multi-stage drawn tubes, cold-headed parts made from drawn wire, or bulk cold-formed components. Intermediate annealing helps regain the necessary material properties.

Metal Deformability and Crystal Structure

Lattice Structure

The deformability of metals can be attributed to their crystal structure. As the melt solidifies, particles (atoms, ions) initially arrange themselves at randomly distributed locations to form regularly structured crystal lattices. While the melt becomes solid, more and more particles attach to the lattice (crystal growth). Occasionally, irregularities occur, which in materials science are referred to as lattice defects. Simple defects include:

• Foreign atoms – take the place of a particle and distort the lattice due to their different size.
• Vacancies – individual particles are missing in the lattice.
• Interstitial atoms – additionally embedded in the lattice.

Dislocations in the Lattice

Dislocations in the crystal lattices significantly influence  material behavior during cold forming. Materials science distinguishes between edge dislocations and screw dislocations. Edge dislocations  occur due to the addition of half-planes within a crystal,  causing neighboring planes, which normally run parallel,  to deviate sideways. Planes running perpendicular to the half-plane maintain their position. Screw dislocations, on the other hand, occur when lattice regions assume an oblique course to bridge missing  components, forming a spiral pattern throughout the crystal lattice.

Influence of Dislocations on Cold Forming

Dislocations weaken atomic bonds, allowing materials to deform. When external forces are applied, dislocations move through the lattice, enabling the metal to take its intended shape. However, as new dislocations accumulate, they begin to interfere with each other, increasing resistance to further deformation. This effect, known as work hardening, gradually strengthens the material.

Recrystallization

Lattice structures are in constant motion, vibrating around their ideal positions, a motion directly correlated with temperature. When the temperature surpasses a critical threshold, the thermal energy allows atomic rearrangement, eliminating many dislocations and restoring the lattice. This temperature is known as the recrystallization temperature, typically around 40-50% of a material’s absolute melting temperature. Some metals, such as zinc (787°F / 418°C), lead (622°F / 328°C), and tin (450°F / 232°C), cannot undergo work hardening because their structures automatically realign after deformation.

Additional Hardening Methods

Grain Refinement

As molten metal solidifies, its crystal grains grow until they meet neighboring grains, forming grain boundaries. Since adjacent grains have different lattice orientations, grain boundaries resist deformation, increasing material strength. Grain refinement enhances strength by controlling cooling rates and introducing crystallization nuclei, increasing the number of grain formation sites. The result is a finer grain structure with more grain boundaries, boosting strength while preserving toughness—unlike work hardening, which increases brittleness.

Precipitation Hardening

Most metals used in industry are alloys, composed of multiple chemical elements. For example, steel is an alloy of iron and carbon, with additional elements enhancing corrosion resistance and mechanical properties. Since different elements exhibit varying solubility in metal lattices, precipitation hardening involves heating the alloy to dissolve alloying elements uniformly, followed by rapid quenching. This process creates supersaturated crystals containing more foreign atoms than the lattice can accommodate. Over time, excess atoms migrate out of the lattice, forming precipitates at grain boundaries, restricting dislocation movement, and increasing strength.

Solid Solution Hardening

Most pure metals are too soft for industrial applications. Alloying elements can be introduced to increase strength by occupying lattice positions (substitutional hardening) or embedding between lattice atoms (interstitial hardening). These additional elements distort the lattice, making it harder for dislocations to move.

Industrial Applications for Work Hardening

Work hardening plays a crucial role in many cold forming processes, improving the mechanical properties of manufactured parts. Modern forming simulations allow precise control of work hardening levels, optimizing manufacturing processes for specific performance requirements.

This effect is particularly beneficial in bulk cold forming, where components such as transmission parts for Ford F-150 trucks, aerospace fasteners for Boeing aircraft, and high-load components in American automotive and defense industries are produced in large volumes within short cycles. Work hardening also benefits wires, tubes, and structural profiles used in construction and steel fabrication.

Work hardening processes have been central to manufacturing in America’s industrial heartland, from Steel Belt manufacturers to aerospace suppliers in Washington state and automotive parts makers in the Southeast. These advanced metallurgical techniques support over 500,000 American manufacturing jobs and contribute significantly to the $2.3 trillion U.S. manufacturing sector.

Der Beitrag Work Hardening Explained erschien zuerst auf Kluthe Magazine.

Application of DIN EN ISO 9227 (Corrosion tests in artificial atmospheres – Salt spray tests)

Corrosion preventatives enable the use of base metals in a wide variety of components. Its effectiveness determines the service life of machines and systems, vehicles, and structures. Manufacturers of such products expect their suppliers to deliver parts that meet defined quality standards. To verify this quality, clear specifications and criteria are required. These are often summarized in the internal standards of major manufacturers. Within this framework, a salt spray test in accordance with DIN EN ISO 9227 may be required. Alternatively, this requirement  may be agreed upon contractually. The standard specifies how the test apparatus must be designed, which substances are used, and under what conditions the test is completed . All other specifications are defined by the company requesting the test from its suppliers. This includes the nature and size of the test specimens, specimen preparation, test duration, and the required results.

Artificial, corrosion-promoting atmosphere

The salt spray test is conducted in a chamber that is continuously supplied with a finely atomized salt solution via nozzles. The standard specifies three variants of the salt solution, each producing a different level of corrosive attack. The neutral salt spray test (NSS test) uses a 5% aqueous sodium chloride solution. A slightly more aggressive method is the acetic acid salt spray test (AASS test), in which acetic acid is added to the sodium chloride solution. The third variant is the copper-accelerated acetic acid salt spray test (CASS test). In this case, the solution contains sodium chloride, acetic acid, and copper(II) chloride dihydrate. DIN EN ISO 9227 specifies in detail how these solutions  should be prepared. It also defines required spray volumes, pH values, and temperatures to be used during testing. These specifications, in turn, dictate chamber equipment requirements for heating, dosing, measurement, and control.

Arrangement of test specimens in the chamber

To obtain reproducible results, the test specimens in a salt spray test must be exposed solely to the  corrosive action of the artificial atmosphere. Other influences, such as contact with other metals or standing moisture on the surfaces, must be excluded. For this reason, there are precise requirements regarding the materials used for the chamber and the racks holding the test specimens. The positioning of the specimens can also influence the results of the salt spray test. The following rules apply:

• as few contact points as possible between the test specimen and the rack or suspension
• no contact between different test specimens
• arrangement of the test specimens at an angle of 20° from the vertical so that condensate separating from the mist can drain freely
• condensate must not drip onto other test specimens

Evaluation and documentation of salt spray test results

The customer specifies which variant of the salt solution is to be used, how long the coating or surface pretreatment of the workpieces must withstand the defined conditions, and which surface changes are permissible. In addition, the customer determines the required characteristics of the test specimens.

After completion of the test period, the specimens tested in the salt spray test are rinsed with distilled water and dried. This is followed by a visual inspection for surface changes. If the salt solution penetrates the conversion coating formed during surface pretreatment, corrosion products form on the base material. This occurs at points where the layer is damaged or contains contaminants. This is evident from blistering under paint and coating layers or from the color and extent of corrosion products. Rust on iron is typically reddish-brown, while zinc forms white, spot-like corrosion products.

It is often of interest to determine how far paints and coatings used for corrosion protection can be undermined by aggressive media in damaged areas. In such cases, the coating is simply scratched, either randomly or according to a defined pattern, before the salt spray test. After the test, it is determined whether and to what extent the coating has detached at the scratched areas.

All observations are carefully documented together with the test duration, the measurement data from the salt spray test, and a description of the test setup, are  recorded in a test report. The observations are then compared with the customer’s requirements. If the changes fall within the specified tolerance range, the test is considered passed.

Informative value of salt spray test results

The salt spray test provides results that can only be used to assess the quality of a surface coating. It allows comparable coating systems on identical base materials to be evaluated. The conditions of salt spray testing differ significantly from the real environmental conditions that corrosion protection must withstand in actual use. For this reason, the test can only provide indirect indications of the corrosion behavior of the tested components. In simplified terms: the coating is acceptable, has proven itself in practice, and therefore also protects against corrosion. This applies primarily to organic coatings such as paints and lacquers, as well as to anodically produced oxide layers (e.g., anodized aluminum). By contrast, the informative value is limited for metallic coatings applied by electroplating or hot-dip galvanizing.

Der Beitrag What Is the Salt Spray Test? erschien zuerst auf Kluthe Magazine.

A Look into the History of Thread Manufacturing

The earliest known references to tools for thread production can be found in the notes of the universal scholar Leonardo da Vinci (1452–1519). Whether they were actually used for this purpose can no longer be determined.

The first primitive machine for cutting screw threads was built in 1568 in France. Seventy-three years later, Henry Hindley of York (1701–1771), a renowned clockmaker and mechanic, improved the design and helped establish screw-cutting for practical use. In Germany, screw forges began to appear toward the end of the 17th century, particularly in Westphalia and the Rhineland, though screws were still largely made by hand.

The idea of standardizing came from British engineer Joseph Whitworth (1803–1887). In 1841, he introduced the Whitworth thread, based on the English inch unit, laying the foundation for modern screw connections. Standardization made screws interchangeable and enabled mass production.

Toward the late 19th century, the first attempts were made to form threads by mass production processes, though this was initially limited to hot forming. American William Keane had already considered thread rolling (a form of cold forming) around 1835, but the steel available at the time splintered during cold working. Only after more ductile steels were introduced did the process gain momentum.

Today, several processes for production are established,  categorized into cutting and non-cutting methods.

Thread Forming with Cutting Processes

The starting material for cutting processes is usually free-machining steel, which offers particularly good machinability. If preformed blanks are further processed by grinding or turning into precision or necked screws, quenched and tempered steels may also be considered.

Cutting / Tapping

A distinction is made here between internal and external cutting. Internal versions are primarily produced using taps. The first step is to drill a core hole with a standard drill bit. The profile is then cut into this bore with a tap. External versions are cut onto a bolt-shaped blank using a die.

Turning

In this process, a cutting tool is used in a longitudinal turning operation. The profile and positioning of the tool are selected according to the desired shape. In multi-stage production, the cutting tip of the tool is applied repeatedly at the same point on the workpiece. The feed corresponds to the pitch. This method can be used to produce both external and internal forms.

Chasing

Thread chasing makes it possible to manufacture economically on lathes and automatic machines. The tools used for this are available as shank, square, and disk chasers for both internal and external use. They are available as single-tooth and multi-tooth versions.

Milling

Thread milling requires machine tools capable of performing movements along the x, y, and z axes simultaneously. This process is mainly used when there are high demands for process reliability and quality. Thread mills are considered problem solvers for special applications. They are rarely used in mass production.

Whirling

Thread whirling is the method of choice where the length is large in relation to the diameter. Also known as thread peeling, this process allows even difficult-to-machine materials to be processed with low tolerances. It is often used to manufacture bone screws from stainless steels or titanium.

Grinding

Thread grinding is primarily used to manufacture threading tools for internal forms. However, it can also be used to produce rolling dies for external ones. One of the biggest advantages of this process is the extremely  high-profile accuracy achieved  by using ceramic-bonded grinding wheels.

EDM (Electrical Discharge Machining)

EDM is mainly used for producing internal shapes in difficult-to-machine materials. The tool electrode, made of brass, copper, or steel, corresponds to the profile and is driven into a pre-drilled core hole in the workpiece.

Thread Forming with Non-Cutting Processes

In non-cutting production, a distinction is made between hot forming (smaller batch sizes, large fasteners) and cold forming (larger batch sizes). All standardized screws and nuts today are produced by non-cutting methods. For safety components, non-cutting forming is often even required. Non-cutting methods bring several advantages:

• no interruption of the grain flow in the material
• lower stress concentration
• faster production
• no chip formation
• fewer cutting errors
• and a smoother surface structure

Rolling

Thread rolling is  often used in screw production. The tools used for this are pressed onto the workpiece with high pressure, resulting in permanent plastic deformation.

For forming to work, the material must be cold-formable. For pointed types, the elongation at break should be at least five percent. The upper tensile strength limit is about 246,000 psi (1700 N/mm²). Typical materials for fasteners with rolled profiles are:

• free-machining and construction steels,
• high-alloy, corrosion- and acid-resistant steels,
• aluminum and copper wrought alloys with a copper content of at least 60 percent.

Sufficient material thickness is required to form in this way. This depends partly on the material itself and partly on the type and depth of the desired profile.

Pressing / Flow Forming

Thread forming by pressing is another process which is used to produce round profiles in sheet metal. A rotating roller is inserted into a pre-drilled core hole while another roller is applied from the outside. The contour is formed in this stepwise process by displacing the material.

What Role Do Cutting and Forming Lubricants Play in Thread Production?

No matter the method—rolling, cutting, chasing, or milling—threads cannot be produced reliably without lubricants. Especially in cutting, the need for lubrication is often underestimated, which frequently results in significantly shortened tool life. Lubricants lower the temperature and reduce friction between the workpiece and the tool, which in turn reduces wear.

Lubricants are indispensable in non-cutting forming, as sliding occurs between the workpiece surface and the tool. Forming lubricants (generally non-water-miscible) ensure that production runs smoothly. They prevent material build-up, which could cause rough surfaces or even tool breakage. In addition, they help dissipate the heat generated during forming. Residual lubricants remaining on the workpiece provide a degree of corrosion protection but often need to be removed before further processing steps.

Der Beitrag Thread Forms – Rolling, Pressing, and Cutting erschien zuerst auf Kluthe Magazine.

Surface Coating with Electroplating

Electroplating uses electrical currents to deposit metal uniformly on workpiece surfaces. The resulting metal layer typically serves to protect against mechanical wear, as corrosion preventative, and/or improve electrical conductivity. Additionally, electroplating can simplify further processing or achieve aesthetic changes.

This technique is frequently applied to steel or stainless-steel components, employing metals with properties suited to the application, such as:

• Copper
• Zinc
• Tin
• Brass
• Nickel
• Silver
• Gold.

Electroplating is not limited to metallic objects; it can also be applied to materials like plastics, ceramics, and glass. . These materials are pre-treated with conductive coatings, chemically applied metal layers, or metal seeds to enable electroplating. Common coating materials used in this process include chrome, copper, zinc, and nickel.

Surface Modification with Anodizing

Eloxal is the abbreviation for ‘electrolytic oxidation of aluminum’. The term itself indicates that only aluminum can be anodized.  This lightweight metal naturally forms a thin but dense oxide layer under oxygen exposure, providing some resistance to corrosion. However, natural protection is limited, especially in the presence of substances like salt or sulfur  dioxide and does not prevent wear.

Anodizing enhances the aluminum’s surface by creating a nearly pore-free dielectric barrier layer, topped with a finely porous, honeycomb-like outer layer. While natural oxide layers are only a few nanometers thick, anodized layers can reach up to 25 micrometers, making aluminum components suitable for harsh industrial conditions and marine environments. The porous structure also allows aluminum to be dyed, particularly when using pure aluminum alloys with a magnesium content below 4%.

Electroplating Process Steps

Depending on the size of the workpiece and specific requirements, different electroplating techniques can be employed. For oversized components that cannot be treated in an electroplating bath, alternatives like dip plating or brush plating are used. In brush plating, the electrolyte is applied under voltage with a sponge.

Other techniques include:

• Barrel plating
• Chemical plating
• Strip plating

The electroplating process generally follows three main steps:

1. Pretreatment

Mechanical and chemical processes remove oils, greases, rust, scale, chips, and grinding dust from the workpiece surface. Multiple rinsing steps follow to ensure a completely clean surface. The pretreatment is completed with several rinsing processes that ensure an absolutely clean surface.

2. Coating

The workpiece is immersed in an electrolyte solution containing the desired metal. Connected to a DC power source, the workpiece acts as the cathode, while the metal anode serves as the source of positive ions. When the current flows, metal ions from the anode deposit onto the workpiece. The duration in the bath and the current strength  determines the thickness of the coating.

3. Post-Treatment

After electroplating, the workpiece is rinsed and dried. Additional steps, such as passivation or chromating (e.g., for zinc-plated steel), may be  added.

Anodizing Process Steps

Unlike electroplating, anodizing does not add a coating but transforms the surface layer of aluminum. The anodizing process involves four steps,  followed by coloring as an optional fifth step.

1. Pretreatment

As with electroplating, this step ensures a grease- and dust-free surface. For components with high aesthetic demands, chemical pretreatment can smooth surface irregularities through pickling.

2. Anodic Oxidation

Aluminum parts are submerged in an electrolyte solution (sulfuric or oxalic acid) with the workpiece connected as the anode to a DC power source. Lead or titanium plates, unaffected by the electrolyte, are used as cathodes. When  the current flows, water at the cathode decomposes, releasing hydrogen, while oxygen reacts with the aluminum to form the oxide layer. The longer the process, the thicker the protective layer, forming capillary-like pores.

3. Coloring (Optional)

The pores created during anodic oxidation can absorb dyes. Since the color embeds within the pores rather than sitting on the surface, it is highly durable and  abrasion resistant.

4. Sealing

After anodizing, the open pores are sealed by boiling the aluminum in demineralized water. This causes the aluminum oxide to react with water, forming aluminum oxide hydroxide. The pores swell from the edges toward the center, closing completely.

Pros and Cons of Electroplating

Electroplating is a cost-effective method offering extensive coating options. It provides excellent corrosion protection and enhances the visual appeal of workpieces. However, the process generates precipitation sludge containing concentrated chemicals, which must be disposed of properly to prevent environmental harm.

Pros and Cons of Anodizing

Like electroplating, anodizing creates a durable, corrosion-resistant surface. Anodized aluminum can achieve hardness levels between 200 and 400 HV, and even up to 600 HV with hard anodizing. The process also allows for vibrant, long-lasting coloring. However, anodizing is limited to aluminum components.

Anodized aluminum’s non-conductive protective layer cannot be easily re-anodized without first removing the oxide layer through pickling. This can alter the dimensions of precision components, potentially rendering them non-compliant with specifications.

Der Beitrag Electroplating and Anodizing: Key Differences erschien zuerst auf Kluthe Magazine.

Wear occurs whenever materials degrade through use. Abrasion is a specific form of wear that results from what is known as micro-cutting. High abrasiveness significantly reduces the service life of machine parts, places undue stress on materials, and leads to shorter maintenance intervals. To prevent this, here’s what matters most.

What Does “Abrasive” Mean?

The term abrasion comes from Latin and literally means “scraping off.” It describes the removal of material through grinding or rubbing. Materials experts refer to a substance as abrasive when it causes a grinding or rubbing effect that results in smoothing, cleaning, or wearing away of metals or other materials. In practical terms, this often applies to abrasives used to grind or polish surfaces. However, lubricants such as oils or greases can also develop unwanted abrasive effects, which must be avoided during machine operation. This kind of wear increases strain on individual machine parts and often results in expensive maintenance. By simply switching to a different lubricant, such wear can often be reduced. The choice of the right cooling lubricant or forming lubricant has a significant impact on the service life of moving parts. Abrasive, as well as adhesive wear, is one of the leading causes of failure in machines with moving components.

What Happens When a Lubricant Becomes Abrasive?

Lubricants can contain hard particles that impair their lubricating properties. Low-quality oils or greases, especially those used over prolonged periods, tend to form clumps that interfere with lubrication. When such particles—or microscopic surface roughness—penetrate the outer layer of a material, abrasion occurs. Under the microscope, characteristic signs of micro-cutting can be seen, such as tiny scratches or grooves. This is also referred to as furrow wear. It occurs gradually and often goes unnoticed at first.

Much like a cave carved by water and wind over millennia, abrasive wear can take time to become noticeable. Highly stressed machine components like gears, roller bearings, or needle bearings are  significantly affected. Choosing an appropriate lubricant is essential for maximizing the lifespan of interacting parts. Even hardened machine components such as gears or bushings are subject to abrasion. However, using high-grade lubricants can significantly extend service life and reduce maintenance and repair costs.

When Does Abrasive Wear Occur?

There are several common causes of abrasion-related wear. It typically occurs during machine startup or under sudden load changes. At low speeds, lubricants often fail to form a protective layer between components. This is especially true in sump-lubricated systems, which only function effectively once the gearbox is running. Not all gears are fully submerged in oil; only once the parts are in motion does the lubricant spread across all gears, shafts, and related components. Until the machine reaches  an effective operating speed, the oil’s viscosity is not enough to prevent abrasion.

When Is a Lubricant Abrasive? Viscosity Matters

The viscosity of a fluid determines how thick or thin it is. Simply put, viscosity indicates how readily a fluid flows. This allows for a direct comparison of different liquids and their lubrication properties. Using a lubricant with too low a viscosity can lead to excessive wear. If the oil is too thin, it cannot form a sufficient separation layer between moving components. Even when gears appear to mesh perfectly, a proper lubricant ensures that the metal surfaces do not  rub directly against each other. A thin oil or grease layer protects the material and prevents premature degradation.

Abrasive wear can be significantly reduced by using additives in oils. These additives help protect surfaces in boundary lubrication situations—especially when the oil film begins to break down. High operating temperatures can also reduce an oil’s viscosity. When separation between moving parts is inadequate and the lubricant behaves abrasively, anti-wear additives offer critical short-term protection.

Abrasive Wear Caused by Particles in Lubricants

Another common occurrence—even in already lubricated machine parts—is the presence of hard particles in oil or grease. These microscopic particles are roughly the same size as the lubrication film intended to protect the metal surface. Because of their size, they can enter the narrow gap between moving parts and can compromise the lubricant’s effectiveness.

Detecting Abrasive Wear

To determine whether a machine is suffering from abrasive wear, a visual inspection is the first step—but microscopic damage is usually invisible to the naked eye. In such cases, an oil analysis provides clarity. This test can detect foreign particles in the lubricant and indicate whether it is time to change the oil.

Preventing Abrasive Wear

Even during the design phase of a machine, abrasive wear can be minimized by selecting appropriate material pairings. Combining metals with plastics, ceramics, or other materials can reduce surface abrasiveness significantly.

Oils should also be filtered before being filled into the system. Continuous filtration during machine operation is also highly recommended. Oil change intervals must be strictly followed, and only certified, high-quality lubricants suitable for the machine’s operational loads should be used. New equipment should undergo system flushing before commissioning to remove foreign materials and even the smallest particles. Seals and access points should remain closed to prevent contaminants from entering the system.

Der Beitrag Abrasive Wear erschien zuerst auf Kluthe Magazine.

Manganese phosphating is a conversion coating process used primarily on low-alloy ferrous parts. It provides excellent corrosion resistance and reduces friction and wear in sliding or rotating applications. This guide explains how manganese phosphate conversion coatings are formed and how they affect the properties of treated parts. These coatings provide excellent corrosion protection and are especially valued for their wear resistance in sliding applications.

Manganese Phosphating Process: How the Layers Form

The main steps in manganese phosphating are:

• Cleaning and degreasing
• Pickling to remove rust and scale
• Activating the surfaces
• Forming the manganese phosphate layer
• Post-treatment through oiling or coating

Cleaning and Degreasing

Cleaning and degreasing are the first step in any surface treatment process. Workpieces often have accumulated cooling lubricant or corrosion prevention residues that can interfere with the chemicals used to build the manganese phosphate layer. The type of cleaner depends on the contamination: alkaline cleaners work well for heavy, greasy deposits, while milder neutral cleaners can handle light residues. After cleaning, a thorough cascade rinse removes any leftover cleaning solution. In this step, the parts pass through a series of rinse tanks while deionized water flows in the opposite direction, allowing the rinse water to be reused for mixing fresh cleaning solutions.

Pickling to Remove Rust and Scale

Heat treatments and welding often leave rust or scale on metal surfaces. Storing parts for extended periods can also lead to rust spots. Since conversion coatings rely on chemical reactions, these contaminants must be removed. Pickling is only necessary if such impurities are present and it is typically done with an inorganic acid that dissolves rust and scale. After pickling, parts go through a multi-stage cascade rinse.

Activating the Surfaces

Before manganese phosphating, the surfaces must be activated. As salts of phosphoric acid, phosphate coatings naturally form a crystalline structure. The activation solution creates nucleation sites where the manganese phosphate crystals can start to grow. These crystals expand until they meet and cover the entire surface. The number and distribution of nucleation sites determine how large the crystals become in the next step. Choosing the right activation agent helps tailor the coating structure for the intended application.

Forming the Manganese Phosphate Layer

This conversion coating takes place in immersion tanks using a solution of diluted phosphoric acid, Mn²⁺ ions (manganese), and other additives. Bath temperatures for this process are typically around 185 °F (85 °C), with immersion times ranging from 5 to 20 minutes. A multi-stage cascade rinse and drying process completes the phosphating. To keep the concentration of process chemicals within the required limits, the bath must be monitored. Dosing pumps replenish chemicals as needed, and any water lost due to evaporation is replaced with rinse water from the final cascade rinse. Sludge generated during phosphating should be continuously removed using a sloped tank bottom to avoid the need for frequent draining and cleaning.

In the periodic table, Mn (atomic number 25) and iron (26) are next to each other. They share similar chemical properties, and their ions are almost identical in size. As a result, the metal surface easily forms mixed crystals that contain both Mn²⁺ and Fe²⁺ ions along with phosphate ions. These ions can combine in nearly any ratio. The crystal size depends on prior surface activation, while the final coating thickness is mainly determined by immersion time and bath conditions. Coating thickness can be controlled very precisely, typically ranging from 0.00008 to 0.0002 inches (2–5 µm), with thicker layers up to about 0.0012 inches (30 µm) possible.

Post-Treatment: Oiling or Coating

Thanks to their fine, porous structure, phosphate coatings based on manganese make an excellent base for subsequent painting or coating. This is why this method is often used as a pretreatment step before applying an organic coating to high-quality components. The coating’s structure also makes it highly receptive to oils and greases, which are used for additional corrosion protection. The parts are dipped in appropriate oil baths, and the protective agents penetrate and remain in the pores.

Typical Applications for Manganese Phosphating

These manganese based phosphate layers stand out for their wear resistance and ability to reduce friction in sliding contacts. For this reason, they are widely used on parts such as gears and plain bearings. For example, automotive camshafts and transmission gears often receive this type of coating to improve break-in wear resistance and ensure reliable operation under high loads. These benefits also apply to forming processes: when parts are to be further processed by deep drawing, wire drawing, or tube drawing, a phosphate layer containing manganese can reduce the required forming force, decrease tool wear, and minimize the risk of cold welding.

Additional features of these coatings include:

• Electrical insulation
• Temperature resistance of up to about 570 °F (300 °C)
• Attractive matte black-gray appearance
• Excellent dimensional stability
• Good flexibility
• Insoluble in water
• Resistant to solvents, fuels, and lubricants
• Strong adhesion
• Environmentally friendly

Typical uses for manganese phosphating range from fasteners and gears, to components for roller and plain bearings, all the way to parts used in valve manufacturing. Industries that rely on manganese phosphate coatings include automotive, general machinery, aerospace, and plant engineering.

In mechanical engineering and firearms manufacturing, black oxide finishing (also known as bluing) is still common. This conversion coating provides temporary corrosion protection and an attractive black finish. Bluing is done with highly concentrated salt solutions heated up to about 300 °F (150 °C), producing smooth layers up to 0.00004 inches (1 µm) thick. However, the strongly alkaline salts used for bluing are classified as hazardous materials. In many cases, the energy-intensive, environmentally taxing bluing process can be replaced with manganese phosphating, which generates less hazardous waste and is easier to manage under OSHA and EPA regulations.

Der Beitrag Surface Treatment with Manganese Phosphate Coatings erschien zuerst auf Kluthe Magazine.

EcoVadis SAS is a Paris-based company, established in 2007, that operates globally to assess sustainability practices within companies. The outcome is the EcoVadis Sustainability Rating. This rating allows participating companies to precisely determine their standing compared to others in their industry and identify areas for improvement. Learn here about how the service works and what the EcoVadis Rating truly entails.

Why EcoVadis Rating?

Many companies strive to improve sustainability for various reasons. For example, the chemical industry is interested in demonstrating to society how it increasingly minimizes the environmental impact of production through green chemistry, achieves social goals, and makes supply chains for raw materials in the chemical sector progressively more sustainable. A challenge in this area is defining measurable goals and indicators to track improvements and make comparisons. EcoVadis helps companies overcome these challenges by providing a reliable assessment and monitoring of their sustainability performance.

Questions that might influence the assessment include:

• Has the company calculated a CO2 balance?
• Does it set CO2 reduction targets?
• How does it  manage finite and critical resources?
• Is there a human rights officer?
• Is there a sustainable waste management and recycling program?
• How are gender equality and occupational safety ensured?
• Are there comprehensive employee training programs?
• Is the supply chain traceable?
• Does the company engage in social initiatives?

Service Management

To monitor a company’s sustainability and rate it through EcoVadis, reliable information on operational standards, treatment of employees, respect for human rights, and environmental protection along the supply chain is needed. The company uses diverse information sources, including client documents, third-party certificates, business partner data, and publicly available information. This data is stored in a secure cloud and protected from loss and unauthorized access, through processing via a SaaS platform. SaaS stands for Software-as-a-Service, a model widely used in customer relationship management (CRM) where it supports process optimization and profitability enhancement. A unique, specially developed methodology is available for sustainability assessment. This methodology enables a comprehensive rating of a company’s commitment to sustainable practices (Corporate Social Responsibility, CSR).

Methodology for EcoVadis Rating and Scorecard Creation

Alongside the EcoVadis Rating, which allows companies to compare their sustainability management with others in the same industry, EcoVadis creates a scorecard. This report details individual results and highlights areas for improvement. Built on international sustainability standards like the United Nations Global Compact, the Global Reporting Initiative, and ISO 26000, the EcoVadis methodology is based on seven core principles:

1. Assessments are conducted by highly qualified international experts.
2. Evaluation procedures are tailored to specific industries, company sizes, and countries.
3. Using all available sources ensures extensive stakeholder input for a reliable rating.
4. Modern Technology enables secure, confidential processes with accelerated processing times.
5. Documentation is transparent and traceable.
6. Evaluation is based on empirically derived and scientifically validated information.
7. Continuous improvement in assessment processes enhances methodological excellence.

The EcoVadis Sustainability Scorecard

The EcoVadis Sustainability Scorecard contains the assessment results, covering four areas that are also relevant to the chemical industry and promote sustainable chemistry:

• Environment
• Labor and human rights
• Ethics
• Sustainable procurement

Twenty-one indicators are available for evaluating individual performance. These indicators generate points that contribute to the company’s overall rating, allowing for easy comparison of sustainability performance across companies. Additionally, the point scores are used for the rating, which is linked to the awarding of recognition medals: Platinum (top 1%), Gold (top 5%), Silver (top 25%), and Bronze (top 50%). These medals can be used in corporate materials for promotional purposes.

Using the Scorecard in Business Relationships

The EcoVadis Scorecard can be requested by other companies to assess if a business partner meets high standards or presents CSR risks, impacting supplier selection. Clients may also require corrective measures from suppliers if needed. For instance, the chemical industry can only truly engage in green chemistry if raw material suppliers practice sustainable chemistry. A supplier’s scorecard provides reliable insight into the standards of its production processes.

Summary of the EcoVadis Rating Benefits

An established methodology with proven technology, quickly delivers a comprehensive assessment of a company’s sustainability, meeting environmental, sustainability, and legal requirements. Self-assessment questionnaires are tailored to company needs, while strengths and improvement areas are revealed through the EcoVadis Rating. Key performance indicators facilitate efficient, trackable improvements, and the scorecard information exchange between companies strengthens business networking.
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Der Beitrag What Does the EcoVadis Rating Indicate? erschien zuerst auf Kluthe Magazine.