has gained a substantial hold in the market over the years. After seeing a year by year dynamic growth in the automotive industry, powder coating is being expanded to be helpful with non-generic surfaces as well.
Powder coating has gained a substantial hold in the market over the years. After seeing a year by year dynamic growth in the automotive industry, powder coating is being expanded to be helpful with non-generic surfaces as well.
Here we talk about the powder coating process of Aluminum. Powder coating involves the electrostatic application of finely ground dry paint film to a specially prepared aluminum surface. The subsequent heating of this film allows the powder to melt, flow out and cure to a tough smooth finish. The powder coating process involves three major stages.
Chemical Processing, also known as Pre-treatment, is what we’ll be discussing with you. The process is a little tricky but fear not. We’ll share with you some tips and insights to give you a headstart.
Pre-treatment is very important because it provides a clear, uniform, oil-grease free surface. It also provides good hold of film and forms an unreactive layer which prevents corrosion. Pre-treatment process should be handled with the utmost importance and care, because the durability of the powder coating depends entirely on the pre-treatment of the substrate.
The pre-treatment process if of two types: Mechanical Surface Preparation and Chemical Surface Preparation. But for powder coating the most commonly used surface preparation method is chemical pre-treatment. The pre-treatment process follows this sequence:
There are a couple of de-greasing methods that are used to clean a surface. The type of procedure depends upon the type of surface and the amount of pollutants on it. Here are some of the most popular ones:
The most cost-effective method, Solvent Cleaning easily wipes off heavy greases or oils from metallic surfaces. In addition to this, the solvent also doesn’t harm the surface in any way, making the method safe for the powder coating procedure. After being dipped in common Alkene solvents, the surface is wiped with a clean cloth.
An innovative method of cleaning, Vapour De-greasing uses purpose-made solvents to get rid of fine oils and minerals. These solvents are not only safe to be used by non-professionals, but are also easily cleanable. The method of use is the same as that of solvent cleaning.
The cleaners used in this procedure make use of solvents with a higher pH, which are completely safe to use at room temperature. These are generally alkene emulsifiers and are suitable for wide variety of surfaces. The objects are dipped into the solvents for a couple of minutes for best results.
Based on strong alkalies, the solvents are used as baths to immense the objects in. However, this method of cleaning doesn’t work with iron based metals, such as Zinc, Aluminum, Glass and Galvanised Steel, because they can get reactive.
Corrosion starts when iron is subjected to damp environments. Even though such rusting is almost unavoidable, it can easily be dealt with. This is because rust can be dissolved using acids, in the process of acid cleaning.
The Activation process is when a metallic surface is provided with active crystal spots to conduct phosphate coating. This helps in ensuring that phosphate covers the surface entirely. Here’s how it’s done:
Cheaper of the two, acidic activation doesn’t require testing and control. You can get it ready in hard water, and the process yields bigger crystals in coating. This is not recommended for substrates containing Iron, such as Aluminum.
Suitable for most substrates, this provides a finer and more resistant finish. The coating is much better than that of acidic activation, and is better suited for Aluminum.
The most popular conversion coating is that of Phosphate. Commonly known as phosphating, this is where phosphates are bonded to the surface. This involves making the surface reactive, providing excellent sticking for the paint. The process is of two types:
Very popular with the automotive industry, Zinc phosphating revolves around a bath containing saturated phosphoric acid, in combination with Zinc phosphate. The acid of the solution targets the Iron particles of the surface, in a chemical reaction, causing the phosphate layer to form.
This is further sub-divided into 3 types:
Cheapest of the lost, the solution in Mono-cationic procedure contains only Zinc.
In addition to Zinc in the solution, this process also contains Nickel, which helps with providing enhanced resistance to rusting and corrosion.
Zinc, Nickel and Manganese are equally involved as cations. Benefits include adhesion, rust and wear resistance.
No substantial cation is involved in Iron Phosphating. The processes contains sodium or dihydrogen phosphate, in combination with catalysts.
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