To get the absolute best performance from your powder coating system, you must properly clean every part before it is coated.
Why? The short answer is that if you cut corners your work will show it. Without proper surface preparation, any type of soil (oils, polymers, dirt, metal bits, soaps, etc.) left on a part will compromise the coating in a variety of ways. Bubbling, streaking, flaking and reduced durability are just a few of the adverse effects of contamination that can ruin your coating – and are avoidable by cleaning. Prepping a part is essential to getting a good finish, but cleaning parts isn’t much fun and it is tempting to take shortcuts. Don’t!
Powder coated finishes are typically much tougher and longer lasting than conventional wet paint, but only if the part is prepared properly. Regardless of the part to be coated, large or small, it must be cleaned thoroughly for the powder media to work properly.
Below are some tips that will help you get started with pretreatment:
Test the Waters
Water quality can have a big impact on cleaning/pre-treatment operations. Particles in the water will inhibit vital chemical reactions, leave unwanted residue on parts or produce soap scum or scaling in the rinse cycles. Water that is overly soft or hard can also produce adverse effects, and water quality can contribute to flash-rusting after cleaning.
It also important to use the right quantity of water for the job. Too little water may mean an inefficient use of chemicals, leaving residues on parts and driving up costs. Too much water is environmentally unfriendly and may use too much chemical, also driving costs upward.
Have your water tested and go over the results with a qualified chemical supplier or engineer specializing in water treatment. Your quality control will be solid from the start. You will produce cleaner parts and save money in the process.
Three Simple Rules For Better Pretreatment
Rule #1: Review your cleaning and prepping process with a knowledgeable chemistry professional.
When it comes to chemistry, consult a professional who SPECIALIZES in pretreatment chemistry. With that being said, do enough homework to understand the major issues of parts pretreatment before you call in a pro.
Rule #2: If you want to have consistently good results, you must set up a cleaning and pretreatment routine that will be sufficient for your WORST parts—not your best parts.
The most important step is to carefully examine the parts you want to clean. You have to be honest about just how clean or dirty your parts really are. Countless coating jobs have been sabotaged because the coater did not adequately prepare the part(s). This happens when the coater only examines a few sample parts and then starts coating.
All of the soil should be removed to achieve a quality finish. Soil is anything that is on the surface of a part. Dirt, grease, oil, shavings, wood, waxes, metal oxides, release agents, you name it. Anything that isn’t powder is soil. It is important that you examine a large sampling of parts so you know how much soil is present on the parts you are going to be coating.
When it’s time to coat, slow down for a moment and look over the part(s) to see if they are still as clean as they were when you completed the pretreatment process. If they aren’t, work on them some more. This is an absolutely critical step on your road to getting top-notch finishes. It can be very tempting to say, “that’s close enough” and coat a part after some rust has popped back up or a grease stain isn’t totally removed. If you don’t give in to temptation, the chances of getting stuck with a re-do are much smaller. Always – always! – check how clean your parts are before you coat.
Rule #3: If it’s organic soil it will probably need an alkaline based cleaner. If it’s non organic, it will probably need an acid.
This is only part of the consideration, though. Oils and greases need not only a highly alkaline-based cleaning solution but, since many industrial oils include types of wax, it is likely that the cleaning solution will need to be heated. Polymers, like silicone, will need an aggressive acid and may also need heat. Many soaps and dry lubricants typically need not only heat and a highly alkaline solution, but mechanical action, as well. Particulates, solid pieces of things like metal shavings, may need an acid/alkaline mix and vigorous mechanical action for full removal. Finally, oxides (rust, tarnish, etc.) will require a finely balanced acid to completely remove the oxide without damaging the surface of the part being cleaned.
Good luck, and remember there is no such thing as a part that is too clean.