Step-by-Step Guide to Powder Coating Process, FAQs, and More

Steps of the Powder Coating Process in Greater Detail

Step 1- Prepping the product surface for powder coating application

1. Prepping the part for powder is oftentimes the most crucial step in ensuring your powder coating results in a strong long-lasting powder finish. Proper prep will depend on a few factors including the product substrate of the part, the condition of the part’s substrate, and the performance requirement for the powder coating.  Will go into this in  greater detail now.
   1. What the product substrate is – The most common substrate for powder coating is carbon steel. However, you may want to consider powder coating other surfaces as well such as wood or aluminum. As a general rule, for powder coating to stick to a substrate, the surface has to be roughened up a bit and cleaned of any rust or foreign contaminant. 
   2. What the condition of the substrate is – If the substrate has rust on it, you will want to remove the rust through sandblasting to ensure the rust doesn’t continue to corrode the product surface after the powder coating has been applied. If the surface has oils or grease on it, you will want to ensure that oils and grease are removed by using a proper degreasing agent, which could range from solvent wipes to a hot water washer with chemical degreasing agents, to a fully automated powder coating rinse line.  

• The Performance Requirement of your powder finish – The cleaner the product substrate and the more uniform and appropriate the profile that you have created,  the longer the final powder coating finish will last and the better it will perform.

Common Powder Coating Preparation Methods

1.) Sandblasting – Sandblasting is a very effective way to prep metal for powder coating, especially if the metal has rust or any previous paint on it.  Sandblasting will remove previous paint and rust while also creating an anchor profile for the powder coating to adhere to.  For small parts, sandblasting can be done effectively and quickly in a sandblast cabinet, making it a simple and cost-effective option.  For larger items, a sandblasting room or outdoor area could be used.

2.)  Wash Bays- Wash Bays are a great option for large batch preparation of carbon steel products that have no surface contamination other than  grease and oil. A wash bay can be used to manually apply a rinse as well as an etching agent like a phosphate or zinc phosphate rinse.  These systems allow you to prep a variety of different shapes effectively in a timely manner.

3.) 3 to 6-stage Washer Systems – The final option for powder coating preparation is using a 3 to 6-stage wash system (more on wash systems is in our guide here).  Wash systems are best used for parts that are made of steel that didn’t have previous rust on them or have been already prepped by sandblasting.  They are best used for parts with relatively similar sizes and weights but a high volume of output is desired.  Unlike wash bays, they will not be as easy to use for a variety of product sizes but will usually allow you to prep a lot of products in a continuous cycle.  The number of stages for a powder coating washer system will depend on the durability you are striving to achieve.  Depending on the protection level your looking for wash systems can vary from a simple rinse and zinc phosphating process to multiple rinse and wash stages along with zinc rinsing for additional protection.

Additional Preparation that may be needed (When to consider Preheating / Off-gassing the part)

If you find you continuously get surface defects in your powder coating finish and you know you’re dealing with parts that have had oil contaminants, you may want to outgas your part.  Outgassing is when you raise the temperature of the oven 50 degrees above the temperature at which you will be curing the powder.  This helps to release any trapped gas or moisture on the product surface. Outgassing is done after sandblasting or prior to using a wash bay/ washer system.  Typically, cast iron and aluminum can have trapping and so they are good metals to be considered for preheating. 

Step 2 of the Powder Coating Process – Applying Powder Coating

After you have prepped the product and ensured you have removed any contaminants including rust, grease, and oil, then you can apply the powder coating.   Applying powder coating effectively requires a few practical things.

1.)  Ensure the product and powder equipment are grounded well

  You will want your powder equipment and the product to which you are applying powder coating  to be well-grounded.  Since powder coating works off the electrostatic principle, in order to get the powder coating on your product as efficiently as possible, you will want to have the product and your equipment well-grounded.  For best results, you should use a ground tester  or  an ohm meter and measure the resistance from a grounding rod to the product.  You will want to aim for 100kΩ or less in resistance (less than 10 is ideal).  Anything over 1MΩ is considered poor grounding.  If you are not achieving  good grounding, you should try using a heavier gauge grounding wire,  with additional grounding clamps attached to the part, or if the clamp is attached to a rack, ensure the racks are clean and are metal to ensure good grounding is achieved. More on grounding can be found here

2.)  Apply the Powder Coating

When applying powder coating, you will want to apply enough coating to cover the entire product.  Depending on the quality level of powder coating you want to achieve, you may want to invest in a dry powder application measurement gauge so that you can ensure the amount of powder you apply is ideal and will provide the right protection.  More on applying powder coating can be found in our video guide here.  A big part of getting great results from your powder coating is setting your powder coating gun effectively for the parts and products you’re coating.  Our guide here goes into details about how to set and adjust your kv and microamp settings to ensure ideal performance.  For wide flat surfaces, keep KV’s and microamps settings high.  For cornered areas, drop kv’s a bit and reduce microamps to a low setting (30 or less is usually appropriate). If you will be doing 2 coats, consider a lower KV and microamp setting, like that you use for powder coating cornered areas.

Step 3 of the Powder Coating Process – Cure the Powder

After the powder coating has been applied, the final step is to cure your powder coating.  During curing, the powder flows out and bonds together to form the protective finish that powder coating is known for.   Typical powders are heated to 350 to 400 degrees Fahrenheit for 20 minutes, though your exact cure schedule will be on your powder coating’s technical data sheet.  Curing powder coating can be done using convection or infrared curing.  Infrared ovens tend to be faster at curing powder coating but they do require parts that do not have a lot of corners or recesses.  Convection ovens are more flexible in the product shapes and sizes they can accommodate.  You can also use a convection/IR combo oven to allow for the benefits of IR and convection curing together.

What if you have two coats of Powder to apply?

Sometimes, you may be doing a dual coat of powder coating, a base color followed by a high gloss finish or something similar. If you are applying two coats of powder, you will want to make each coat 3 mils or less in total powder applied.  If you apply more than 3 mils, the second coat may not stick or it can create a build-up of electrostatic charge and result in back ionization (which will look like a starburst in the powder).  To perform a recoat, you will want to reduce the KV and microamp settings on the second coat.  Additionally, it can sometimes help to heat the first coat of powder until it gels out and then remove it from the oven and spray the second coat while the first coat is still in a gel state, this is known as hot flocking. 

Final Thoughts on the Powder Coating Process

Overall, powder coating is a pretty simple concept.  A part is properly prepared to ensure the surface is clean and has a profile for powder coating to stick to. The powder coat is applied with a powder coating gun using an electrostatic charge, and once applied, the powder coat is cured to ensure a durable finish.  By following the tips and principles in this powder coating process guide, you will ensure that you get consistent quality results.