Powder coating is an excellent way of protecting metal surfaces. It produces a brilliant and more durable finish than wet paint. It is also more environmentally friendly. Sometimes, though, you’ll see it chipping off. This can be disappointing as it really doesn’t look good. Chipping will leave the metal exposed to corrosion, allowing your parts deteriorate quickly. If powder coating is so strong and durable, what causes it to crack or chip off?
In this blog post, we’ll explain how this happens and how you can avoid it from happening to your parts.
Composition of the Substrate
The powder coating system consists of layers where each stage of the process can impact negatively on layer. For example, if there was a problem with metal surface this may affect the surface preparation step of the system and finally the powder coating itself.
Poor Surface Preparation
If a surface is not properly prepared before it is powder coated, the surface may be contaminated with oils, paints, chemical sealers, and it can cause the powder coating to have substandard adhesion, which cause the coating to crack or chip. To ensure the best possible powder coating finish, you need to make sure your surface preparation processes are thorough. These processes can include cleaning the material, stripping away any corrosion, rust, dirt, oil, degreasing (if applicable) the surface, and creating a surface that the powder coating can adhere to.
There are two main types of surface preparation methods:
Mechanical preparation by using abrasive blasting equipment or manual sanding by hand.
Chemical pre- treatment before powder coating.
Both these processes must be done properly to extend the life of your powder coating.
Poorly Prepared Edges or Corners on the Part
The most common reason for your powder coating to chip or crack is because the edges or corners of the part have not been surface prepared properly. Edges and corners are difficult to powder coat, and sharp metal edges may poke through the coating. It is best to “break” or linish all edges smooth to allow full coverage.
Incorrectly Cured Coating Film
One of other reasons for a non-durable powder coat finish is that the powder is under-cured. However, over-curing can also produce similar results. When a powder coated part is curing in the oven, it goes through several stages of curing and if you remove the part from the oven too soon and/or the temperature is too low in the oven, then the powder cannot complete its full cure cycle. This often leads to a powder coat finish that easily chips or cracks.
There are various ways to repair a part that is chipping due to under-curing/over-curing, which could even require the complete stripping of the powder coat and re-do it.
Powder Coat Applied too Thick or too Thin
If the powder coating is applied with too much or too little powder, problems can occur. If a part is powder coated too little, the surface will be patchy, unprotected, and will corrode easily. If too much powder is applied, it can result in poor adhesion and coating will be thin and possibly porous. It may crack, bubble, or peel. Over or undercoating also can lead to imperfections in the finish.
Even if the material is properly powder coated, there is a possibility that it will wear from environmental pressures. If your powder coated part/product is in extreme heat, cold, or around rough substances such as water, dirt and/or salt particles, it may corrode faster than you intended. The environment will slowly wear down on the powder coating, and it will end up being less effective at protecting your equipment.
Arkote - Your Trusted Surface Coating Partner!
No paint lasts forever, but we can repair powder coating that has failed so that metalwork looks as good as new again.
If you’re looking to apply a powder coating over an existing one, it would need to be relatively fresh and cleaned to get good results. We recommend to completely strip the old coat, as that will offer better quality than applying another powder coat on top of a damaged coating.
Not sure if your project qualifies? Arkote can help you evaluate your object and let you know. Contact us to discuss your surface coating need with us on (08) 8276 8811 or click on the button below to request a free quote online.