Everything You wanted to Know About Powder Coating
Whether you’re a hobbyist or a production facility considering powder coating it can often be a confusing process getting familiar with it. Terms like parts washers, electrostatic powder coat guns, and spray to waste or powder recovery can be a lot to consider and learn. This guide will serve as a comprehensive resource on what powder coating is, what is required to powder coat, how powder coating is done and additional information
What Powder Coating Is
Powder coating is a process that applies a dry powder to a products surface. The powder is applied to the products surface by electrically charging the powder and grounding the intended product. The charged powder will by nature be attracted to a grounded product, in this case the product surface, and as a result will create a bond between the powder and the product surface. The electric bond holds the powder to the products surface until the powder can be cured which will cause the powder coat to flow out into a smooth finish. Powder coating has a variety of pros and cons which you can review here to better understand if powder coating makes sense for your product or project needs.
What Is Required for Powder Coating
To begin powder coating you need a powder coating gun, an oven that will provide sufficient heat for your part, a place to apply powder safely, and when applicable a way to properly prepare your part for powder. There is a great range of equipment that can be used for powder coating. Will cover the key equipment you need and typical differences in quality levels.
Powder Coating Application Equipment
With higher quality powder application equipment, you get equipment that is rebuildable, will offer programmable options to help with issues like far-a-day-cage effects, and will typically provide a better powder fan which can result in an improved finish appearance. Industrial grade units like a Wagner Powder Coat Unitwill also offer a variety of powder feed options like box or fluidized bed units which are also suited for higher volumes of powder unlike smaller cup fed powder coating units. The powder coating controller will allow for adjustment of the KV or micro amps to resolve issues with far-a-day cage or to allow for multiple coats to be applied to a product if needed. Powder coating Guns are commonly offered in tribo or corona design with each carrying specific benefits and drawbacks. For a great overview of Corona or Tribo design powder guns you can review our guide here.
Powder Coat Curing Ovens
There are two primary ways that powder coating can be cured one being via an infrared oven and the other being with a batch convection oven. The differences between the two are the speed at which they cure, the way they cure, and energy they use. For additional information on convection vs infrared ovens you can read our guide here. Industrial quality batch ovens whether they are infrared or convection ovens provide use for many years, consistency in the heat or energy wave that is produced by the oven, and consistency in the cure that is achieved. Additionally they are typically safer in design.
Powder Coating Booth
For safety consideration NFPA 33 Section 15 section 6 recommends one of two options for applying powder coating. One is a powder booth and the other is an enclosed room that meets specific requirements you can review those requirements through NFPA 33’s website though a booth will be the easiest way to ensure you have properly met all safety requirements. A powder booth can also be fitted with a powder recovery cartridge that allows for you to recover powder media cleanly and effectively or for high production needs you can integrate quick color change out powder modules that allow for switching of colors quickly (this is typically for conveyor lines with very high production needs).
Surface Preparation
Preparing for powder coating can have a variety of requirements depending on your powder coating application. If the part you will be powder coating was pre painted or has rust you will typically sandblast the surface to remove all previous applied coatings or any rust that has formed.
Surface Cleaning and Treatment
If your working with original metal without any contaminant or if you cleaned a surface with sandblasting you will have to remove oils and similar contaminant prior to applying your powder. A variety of options are available to clean off oils and grease prior to adding the powder including solvent wiping, pressure washing, dipping or automatic washing of the surface. Of these options automatic washing is usually well suited for high production. Solvent wiping is typically for very small projects and pressure washing can be an option for smaller projects while dipping can often meet needs in between.
After removing grease and contaminant from the surface a final stage that is often done prior to applying powder involves etching, phosphating, or a more modern option called Zirconium Non-Phosphate pretreatment.
Etching uses a chemical that cuts the surface with an acid which allows for improved adhesion of powder which is particularly helpful with metal surfaces that are slippery.
Phosphating washes the surface to create a better surface for adhesion and also helps improve the corrosion resistance of the surface. It is one of the original ways of treating a surface prior to powder coating. The zirconium process involves a balance of etching and protection.
What To Remember
The preparation of the surface will depend on the goal of your powder coat. Etching improves powder adherence so for indoor equipment that may be bumped frequently an etch can make sense as it will help the powder remain on the surface longer. For an outdoor product like a rim you may need to blend both adherence and protection ( an acid etch and phosphate process together). For something that will rarely be interfered with just a basic powder applied to the surface and cured can meet your need. If you have additional questions about powder coating or powder coating systems you can contact us today.