All right. You have decided to start powder coating. For most of you, this is an exciting and scary time. With the purchase of the powder equipment and the arranging of where to put it, you probably haven’t had a lot of time to think about the small stuff. So this article will give you some basic supplies tips that will get you coating faster. There are also so industry specific supplies or requirements to consider, but that will be at the end of the article.
Some supplies are fairly self-explanatory. If you are blasting to clean your parts, you will need some sand, garnet, or shot to run through the machine. Don’t buy a lot at first of any specific brand or size because you might wind up switching materials after a week. Buying the minimum amount to test your cleaning process is usually the best idea. The same goes for pretreatment chemicals, if you plan to use them. Most suppliers of chemicals will sell you a small amount to try before you commit to a large order. Sometimes they will even provide small samples for free. It doesn’t hurt to ask for a free sample.
After you have decided how to clean your parts, you will need to hang them in order to transport powder coated parts from the powder booth to the oven with out rubbing the powder off. Racks can be purchased or home made depending on your metal fabrication skills. If you are buying or making, the most important part of a rack is the wheels. Make sure you have metal casters at the bottom of the rack, that can withstand 450 degree heat. Order or make enough racks that you have at least one rack per finishing step. One in blasting ready for loading, one in the powder booth, one in the oven, and one in cool down or in your off load area. You don’t need that many to start powder coating and you may want to test one or two rack set-ups before you commit to buying or making four or more.
While you are experimenting with your rack design, try some different hooks. Get some samples from hook manufacturers or make some hooks using some bar stock and a wire/pipe bender. Most manufacturers do not use the first type of hook they try. You want a hook that will not get in the way of the powder, that will support the part, and be conductive for a proper grounding of the part. Plan on replacing or cleaning hooks every 5-6 uses. The reason for that is to keep a good ground on the part so that the powder does not fall off easily when moved or when a draft of air hits a powdered part.
Air cleanliness is very important to powder coating. Make sure you have a good oil/water separator on your incoming air line to make sure the powder is clean before it hits your powder gun and the powder that is being applied to your parts. A dedicated compressor with an air drier is ideal, but a decent filter on your air line will stop moisture from hitting your powder.
Now that you have clean parts on racks, they are ready to be powder coated. Most new powder coaters start with polyester powder coating. Polyester powder is user friendly, durable inside and outside, fairly inexpensive (except for wild colors and effects), and cures in an oven reliably without a lot of fine tuning. All powder companies have standard color cards that you can order from that cover most industry colors. If you know exactly what powder you will be using, then get a weeks worth of production quantity at a time. Most powder companies have 2-3 days shipping times on standard colors.
While you are ordering powder, don’t forget to get some extra booth filters. One set of the first layer of filtration should do, be they filter squares or blankets. The other filters like bag or HEPA filters should not wear out very fast and can be ordered when needed. Remember not to “blow out” dirty filters with compressed air. That will cause holes in the filters and allow powder to get to the secondary filters faster than it should. Although the booth will pull most of the powder into the filters, operator masks are still required. According to the Occupational Safety & Health Administration (OSHA), Washington, powder coating workers must wear no less than what is called an “N95,” NIOSH-approved respirator (otherwise known as a dust mask).
Depending on the powder gun you have purchased, there will be different wear parts to keep on hand to keep you gun spraying properly. Powder pump(venturi) nozzles, gun tips, and extra hoses are the most common extra powder coating gun supplies to keep around. The nozzles are near the pick-up tube and are necessary to keep the powder flowing without surging. They are plastic, so powder will eventually wear them out by cutting into the side. If you see a groove being cut into a nozzle or if the nozzle starts to look oval in the middle, change it out. Gun tips typically don’t wear out, but operators do drop guns accidentally so it’s a good idea to have a spare or two. Hoses can get holes, be run over, get cut, or be melted by a hot rack. I’d have a couple around just in case. Some folks keep an extra set of hoses for color changes.
While you are in the powder booth area, there are a few other things that might be good to have around. Silicone plugs and high temperature tape will keep powder out of areas or off surfaces that you don’t want powder coating on. Bolt holes and friction surfaces are a couple of places you would want to keep powder away from. A box of cheap ear plugs are good to keep in the powder area. Safety-wise it’s a good idea to wear ear plugs in a noisy environment like a spray booth. Unused ear plugs are also great hose scrubbers for using between color changes. By using compressed air, you can shoot an earplug through a powder hose to “scrub” stubborn powder off of the interior hose walls.
Before you start moving racks in and out of the oven, you will want to invest in some high temperature gloves or mitts. 400 degrees F is pretty hot and will burn you if you don’t take precautions. Keep some high temperature grease close to grease the bearings of the fan in the oven.
After your parts have cooled down from being baked, it is a good idea to regularly check your finish to make sure it meets your quality standards. The easiest test is an MEK rub test. By getting some MEK and some q-tips, you can spot check your parts to see if you are getting enough cure. 20 double rubs will let you know if you have enough cure. Adhesion testing is also done fairly easy although you will want to check it on a scrap piece of metal instead of a part. Use a utility knife and some sticky tape to do a cross cut with about 5 cuts each way. Apply the tape to the cross cut and then pull up the tape. If any squares come up you need to look at your metal preparation or your cure. The final tool in a basic quality control box is a dry film thickness gauge. Be sure and get one that will measure steel and aluminum. Checking powder thickness is important for ensuring durability and to reduce unnecessary powder waste.
Those are the basic supplies or additions that every industry should think about incorporating in their process. Next up are some additional supplies or different materials that you might need for specific industries.
All architectural aluminum finishes will have to be pretreated with a Zirconium based pretreat and something to take off the oxidation of the aluminum. The powder used for extruded aluminum is usually of two different qualities. The first is Superdurable Polyester AAMA 2604 quality. This is what most architects will specify for the exterior of buildings. KYNAR® AAMA 2605 quality is the most durable exterior powder for powder, however, it is very specific on how the pretreatment must be applied. KYNAR® can only be applied over an automatic pretreatment system specially designed for these 10-30 year warranty finishes. Since the warranty is so extensive, an on-site boiling water test is usually added to the quality control daily checks. A color computer or unit is usually required because customers need verification that the parts produced will match other components done at different manufacturers.
Heavy Exterior Equipment
Heavy equipment suppliers usually will need upgraded exterior durable finishes. This starts in the pretreatment. While a one stage pressure wand may work in most cases, there may be additional steps depending on the end customers specifications. 3-5 stage systems may be needed to insure proper salt-spray requirements. A wash stage, rinse stage, phosphate (iron/zirconium/zinc) stage, rinse stage, and sealer stage is a common set-up. Additional testing like impact or salt spray are usually done on-site or by the powder suppliers lab.
Powder coating industrial pipe is an interesting process since they usually heat the pipe to curing temperature and then spray or dip the pipe with powder. This uses a specific kind of powder called Fusion Bonded Epoxy powder. Since the pipe goes underground, the epoxy gives the best durability versus rust, chemicals, and moisture. However, if the pipe is exposed to the sun, polyester powder will have to be applied over the epoxy to keep the coating from degrading due to the UV rays.
Marine equipment like cranes on ships are the toughest environments for any coating to survive. Daily exposure to salt water and extreme temperature changes can wreck any finish. The pretreatment will have to be a 5-7 stage zinc phosphate system followed by a zinc-rich epoxy powder primer. Then a urethane topcoat will be applied to allow the best flexibility and UV resistance protection available. This is not a cheap system and will need regular salt spray and QUV testing by the manufacturer or their powder supplier.
Automotive part manufacturers are usually grouped into under-hood part and exterior part suppliers. Under-hood parts are usually coated with epoxy powder due to the great chemical resistance epoxy provides. Since chemical resistance is so important, regular watch glass checks with hydraulic and brake fluid are not uncommon. Exterior parts are usually urethane or superdurable polyester powder. Gloss and color are very important for automotive manufacturers so daily gloss checks with a gloss meter and color checks from a color unit are usually required. Flexibility and dent resistance is also checked by having impact drop testing and a conical mandrel bend test.
Military powder coating is fairly new. They have a two coat system usually starting with an epoxy powder primer and a CARC powder topcoat. CARC stands for chemical agent resistant coating. It is designed to be resistant to chemical warfare chemicals and also aids in the decontamination process if the vehicle is exposed. All the parts need to be pretreated with zirconium. A gloss meter is usually required to make sure the low gloss is within standard.
Developing your supplies list to tie into your powder process. Don’t be afraid to try different suppliers or qualities of each item. All of your supplies should contribute to a more efficient process and a quality finish. Try and compare each item apples to apples to see how much use you get out of it and if it helps your end customer. Keeping good notes on when you used an item and how much life you really got out of a particular spare part will guide you on keeping costs low and quality high.