Archive: Jan 2023

What are the Different Types of Powder Coating Paint?

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Powder coating paint can be divided into two main categories; thermoplastic powder and thermoset polymer. Both types of powder coating paint require heat in order to flow and form a uniform film. Each type of paint has its own unique chemical properties and method of application.

Thermoplastic powder is generally applied with a fluidized bed process. No electrostatic charge is required. This type of paint is usually applied to a part that is heated to a temperature well above the powder’s melting point. The heat causes the powder to melt, adhere to the part and form a scratch-resistant, uniform film of paint. Unlike thermoset polymers, thermoplastic powders remain chemically unchanged throughout the process, which means that they can be re-melted and reused.

Polyester-based thermoset polymers are often used on items that are continuously exposed to the elements.
Thermoset powder coating paint differs from thermoplastic powder in that it undergoes a chemical change, called crosslinking, as it cures. After it has been heat cured, this type of finish cannot be re-melted or reused. Thermosetting polymers tend to be more durable than thermoplastics and offer a wider variety of finishes.

There are four categories of thermoset powders that are based on the type of resin used as their base. The four basic resins used for thermoset powders are epoxy, acrylic, polyester and fluoropolymer. In manufacturing thermoset polymers, the resins typically are first ground into a fine powder to make them suitable for spray gun application.

Epoxy-based powder coating is resistant to both impact and scratching. Its inability to stand up to bad weather and ultraviolet rays generally limits its use to indoor applications. Epoxy powder coating paint is generally used for coating home appliances, automotive underbody parts and industrial equipment. It also is a popular choice for painting metal furniture, such as bed frames and futons.

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Which Alloys Are Prone to Corrosion, and How Can We Prevent This?

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Some exposed metallic alloys, such as those used in electromagnets, are prone to corrosion and may disintegrate into a powder even in clean, temperature-stable interior conditions if not adequately treated to prevent corrosion.

Do All Alloys Corrode?
Almost all alloys corrode or rust to an extent. Corrosion is a type of oxidation, and rusting is a component of corrosion. Rusting occurs when the alloy is in contact with air and humidity, resulting in the formation of an iron oxide coating. Corrosion happens when alloys are exposed to oxygen and chemicals, resulting in the development of metal oxides or salts.

Corrosion Occurrence in Steel

As standard steel is made up of a variety of metals, including iron, it can corrode. Stainless steel, which is 18 percent or more chromium, creates a protective coating (chromium oxide) on the surface of the alloy, while a vanadium concentration also plays a substantial role in preventing corrosion.

Corrosion in Aluminum and Magnesium

Aluminum alloys do corrode, but when water comes into contact with the metallic surface, it develops a protective coating called ‘aluminum alloy oxide’ which makes it more corrosion resistant. Magnesium is prone to corrosion (especially galvanic corrosion), which appears as a grey layer on the surface. Out of all metallic alloys, magnesium alloys have the worst corrosion resistance properties.

Do Zinc and Nickel Corrode?

When zinc is exposed to air, it interacts with carbon dioxide to generate a zinc hydroxide film. This shields the metal from external air reactions, which is why zinc is used to galvanize other alloys and prevent corrosion. Pure nickel is extremely corrosion-resistant, particularly when exposed to a range of reducing agents. It is resistant to oxidation when it is alloyed with chromium, resulting in a wide range of alloys with excellent corrosion resistance in both reduction and oxidation conditions.

Types of Corrosion in Alloys
Corrosion is the result of a series of often complex chemical reactions that may be induced by a variety of factors, that depend on the setting. Uniform corrosion is the most typical form of corrosion, described as an even attack over a material’s surface. It is the most innocuous since the attack is mild in intensity, making the impact on material performance simpler to measure and analyze due to the ability to consistently repeat and test the phenomenon.

Read more: Which Alloys Are Prone to Corrosion, and How Can We Prevent This?