Every day we use products made of metal such as kitchen utensils, furniture, tools, electronics, and vehicles. While paying attention, all their metallic surfaces are covered by different kind of coating.
Why metal need coating?
Metal needs coating for a variety of reasons. Coating metal can protect it from corrosion, UV rays, and other environmental factors. It can also provide a decorative finish, add strength, and reduce friction. Coating metal can also improve its electrical and thermal properties, making it more suitable for applications.
What is the common coating?
You can always identify the unique coating you need for your business or project. Here, I’ll offer a few highly popular coating systems for use in daily life and industry.
Anodizing is a technique used to encourage the development of a protective oxide coating on a metal’s surface. Anodizing boosts corrosion and wear resistance. This popular and frequent surface treatment for aluminum can give items’ surfaces a colorful appearance. But keep in mind that anodizing steel is impossible. The coating is thin and looks like from the base metal, sometimes you may ask why the aluminum has color.
A process for creating a protective zinc carbonate layer is galvanizing. It resists flaking off and is strong. It is a very popular coating for outdoor hardware like nails and brackets. The base metal can receive a sort of cathodic protection from the zinc coating that helps the component endure in a damp environment. However, because the galvanizing coating is expensive at larger scales, you might only find small parts with it. Go to and find some hardware, they have galvanized coating.
By use of electroplating, a thin layer of precious metal is applied to the surface of the base metal. This coating is perfect for decorative components like jewelry since it has good corrosion resistance and gives a great surface finish. However, electroplating is costly and typically results in extremely toxic wastewater that is bad for the environment. Just look at your key chain, that should be electroplated.
In powder coating, items are sprayed with powder, which is subsequently dried in an oven. The coating is often attractive and long-lasting. But you can’t get a uniform, thin, and smooth covering. The spray tool and oven will have a significant initial setup cost but are good for mass production. Unlike the Check metal panels on your appliances, they should have powder coating on it.
Nitrocarburizing, case hardening, polishing, and salt quenching are all included in the quench polish quench (QPQ) process. This process produces an even, thick coating of iron oxide, increasing wear resistance and corrosion resistance. Check your gun barrel or hardcore tools, if the color is black, you probably see QPQ coating.
Epoxies have a thick, smooth layer that often seems plastic-like. This coating has exceptional corrosion resistance. However, cracking is the main issue for epoxies coating while being utilized outside under sunlight due to low UV resistance and the thick coating layer. The coating is better for submerged industrial applications, like subsea equipment.
Teflon, which is frequently used on non-stick pot coating, is comparable to the Xylan coating. Increased wear resistance, less friction, and non-stick are the same functions. Because of this, Xylan coating is frequently used in hardware and other applications where mating surfaces rub against one another and require lubrication.
How to choose coating system?
Metal pieces need to have a good coating. Understanding each material’s qualities and weighing cost and performance are necessary for choosing the best coating. There are several issues you need to consider and also ask your vendor: How long does the coating last? What is the environment the coating good for? What is the coating thickness and how it affects part geometry? What test the vendor can provide to validate the coating? After getting all answers, you can make the decision.
Did your vendor apply the coating correctly?
Preparation is very important to get the coating right, make sure your vendor has the right procedure for this. Don’t save on these steps, otherwise, you may redo it soon or face unhappy customers.
Before coating the following step is typically followed:
1, get rid of all the rust or previous coating. You need to apply the coating to the bare metal. If there is rust between the coating and base material, the corrosion can develop faster due to trapped humidity.
2, degreasing using solvent cleaning. Lubrication and wax may form a thin layer above bear metal, it is hard to notice but will keep the coating from forming a good bonding. A solvent is the best tool to do the cleaning job.
3, clean with tap water to remove the solvent. Tap water and remove all the debris. Make sure to wipe off or dry your component quickly. Keep in mind, part of the water will be corroded, so don’t let the water stay on the part.
4, The coating temperature shall be controllable. Coatings have applying temperature and cure temperature. It is very important that the factory or coating room has ac system to control temperature.
What quality control test you may use?
Adhesion test, all the hard work for coating preparation is to make sure the coating sticks on the part right. So using the adhesion test to verify you get the qualified coating on the parts. There is a standard for you to reference ASTM D3359, use method A or B to verify your adhesion. If the part will slide against other parts very often, stick with the higher-end standards.