If you are thinking of a 'do it yourself' powder coating job, please read David's Powder coating kits page
This is an attempt to clear up some of the mis-conceptions about Powder Coating. I have been in the industrial paint and powder business for more than 20 years. You may well find a specific situation which contradicts what I write, the world is filled with anomalies. This Faq is meant for those that want basic, general information, before they run out to (or run back from!) where they have their cherished bike parts powder coated! I originally started to write this for the Brit-Iron list, but I have received similar requests from the BMW, Vintage Japanese and two stroke lists, so here goes…….
What is Powder Coating?
Simply put, powder is paint applied by a different method. Most all powder paints start life as a liquid, very similar to spray paint. This is where the resin, various components and pigments are mixed into a homogenous mass. From there they are partially cured, converted into a solid, extruded and ground (cryogenically) to the desired level. Colour matches are much more difficult with powder, as once it is made into the powder coating, it is done, versus paint that can have additives used to give desired effects (colour tint, gloss, levelling, texture etc.).
There is a gross misconception out there that powder is some space age material akin to high tech ceramics and carbon fibre. That’s generally not true. Powder is just another method of laying down an organic film, i.e. paint. A powder coating of epoxy will have the same basic properties such as poor UV (sunlight) resistance as a liquid paint. For our purposes, resin types should be limited to Acrylic, Polyester, TGIC Polyester and Urethane resins. These are the systems that have the best UV resistance which equates to gloss retention outdoors.
Most powders have very good chemical and corrosion resistance, but again it is resin specific. Epoxies have excellent chemical resistance. Polyesters and Urethanes are typically used for aesthetic coatings on Cycles and have good resistance. Powders do have an advantage over liquid paint here. If you can, imagine how a liquid coating dries or cures. Solvent has to escape from the film as it "dries down". If you were to look at this under a microscope, you would see a bunch of little pinholes that look like small volcanoes. This is an avenue for moisture and chemicals to penetrate the film more quickly, accelerating corrosion. Powder simply melts down at cure temperature and (usually) isn’t prone to pinholing. Castings are the exception here. They should always be coated after pre-heating so that the pores of the casting don’t "out gas" during the cure cycle. Typical powder cure cycles are 325-375°F @ 12-20 minutes, metal temperature. Actual oven temperature may need to be substantially higher to get the metal to temp in a reasonable amount of time.
Powder coating was introduced to the United States in the late 60’s. It started to really take off in the mid 70’s and has steadily gained in popularity for a number of reasons.
Powder coating is environmentally friendly. Powders contain no solvents (in the final form!) and thus have very low air emissions when curing. Typical powders have a VOC (Volatile Organic Compound) rating of <1.0 pounds per gallon (there is an EPA test method for this!) versus liquid paints in the range of 2.5-7.0 pounds per gallon. There is very little waste with powder. Powder over spray can be collected and reused, rather than just thrown away as with paint over spray.
Powder coating is easy to do. It is much easier to become "good" at applying powder than it is liquid paint. Clean up is also much easier, you can use an air hose instead of solvent.
How is it done?
Powder is sprayed (and in some cases dipped) on parts where it clings by static
electricity (sort of like dust on your TV or monitor). That is where the term
"Electro-statically applied comes from By the way, "electrostatically applied" powder or
liquid says nothing about the quality of the workmanship or material, it is
just a method! . From there it is baked, where it melts, flows and cures.
How should the surface be prepped?
I would leave this up to the coater. If he doesn't give you a warm fuzzy feeling about his ability, find another coater (shipping isn’t that expensive!). In general, most coaters that I know wouldn’t coat over anything on the parts already (especially primer!) so don’t waste your time or money trying to "get it ready".
Powder coating is no different from any other "compliant" coating. What that means is that when the Clean Air Act went into effect, many of the older paints that had a lot of solvent (high VOC) in them were no longer able to be used. These older, high solvent paints, had the ability to "cut through" thin layers of oil or soil and bond to the metal. As newer coatings were introduced such as water based, high solids/low solvent, powder and E-coat it quickly became apparent that these coatings required very clean substrates for good adhesion and performance. Powders are not unique, but they do require a clean surface as does any modern coating.
My preference for surface pre-treatment would be to find a coater that is experienced, and let them do the work. Here is the way I would process items (assumed rebuild of an old bike) prior to coating:
#1. Sort and segregate, by metal type (aluminium, zinc vs steel).
#2. Cleaning and rinsing. Clean steel parts in a hot alkaline cleaner / paint stripper to remove heavy oil, grease old paint, etc. Aluminium and zinc parts can only go into multi-metal type cleaners that are safe for those metals.
#3. Burning. At this point (or instead of #3) many coaters recommend a "burn" to remove leftover oil and grease, especially from frames. I am really against this method unless the operator is an expert at doing it. To do it right, you need a controlled pyrolysis oven (brand names to look for are Blu-Surf, Bayco, Pollution Control). These ovens control the UPPER limit of temperature that the parts will see, some by injecting water, similar to a sprinkler system. Setting the oven temperature is not good enough. Where ever you have a gob of grease or paint, these areas can actually ignite and cause very hot spots on the parts, burning the steel causing fatigue. It is an excellent way to get a part clean, but at what cost down the road?
#4. Blasting. Abrasive media blasting is an excellent way to remove old paint, rust and to increase paint/powder adhesion, as long as it is done properly. Doing it properly means to protect areas that shouldn’t be blasted (bearing raceways, machined areas, etc.), using the proper media (avoid steel media - use silica sand, aluminium oxide, plastic media, etc.) and removal of ALL grit after the job is done. It is very important that the Blaster clean the parts prior to blasting and that he tells you he does it to all customers parts. The reason is that blasting re-circulates the blast media (and some of what has been blasted off). Parts that have residual oil on them will only push that oil down into the pores to come out later when baking, potentially ruining the job, or resulting in premature adhesion loss or corrosion. If he only cleans your parts prior to blasting, chances are that re-circulated media will be contaminated re soiling your clean parts.
#5. Phosphatizing and subsequent rinsing. This is a topic I could write another whole paper on. Basically iron or zinc phosphatizing aids greatly in paint / powder adhesion and corrosion resistance, especially on parts that are not blasted. What it does is to lay down a coating of metal (iron or zinc) in a crystalline form. This chemically bonds to the steel. The coating then soaks into this sponge like layer providing excellent bonding (adhesion) to the steel. Not all places will offer it as it can be a headache for a rebuild type shop, and it is not absolutely needed, but it is worth it if available, especially if redoing a classic that you want to last for a long time. Rinsing after any of the chemical stages is critical. Without proper rinsing you will leave chemicals on the parts that can cause rust later, interfere with coating adhesion or show through the coating in the form of a stain.
Masking
Protect the areas where the head races go, protect the triple crown stem, threads and bearing cup areas and protect the open end of the swingarm so bushings will fit without undue hassle. There are many ways to mask parts that need to be protected from the coating. Silicone rubber masks, high temperature tape, Teflon tubing, magnetic metal masks all work well. One of the really unique things you can do with powder, especially on a one at a time basis (versus a production line) is to coat the whole thing. Then selectively blow off the areas to be masked with a fine tipped air nozzle. I have used this method many times, and is a lot easier than picking off adhesive tape masks after curing! If you screw up, you just blow the whole thing down and re-coat. It does require some practice / experience, but it sounds much harder than it is.
To Coat Or Not To Coat?
Almost any metal part than can be painted, can be powder coated, with a few caveats. In order to use powder, parts must be able to withstand the curing temperatures of powder. This usually means 350°-450°F for 15-30 minutes. This pretty much rules out plastic substrates and things that might warp like cylinder heads. Low cure powders are being developed for use on plastic substrates, but for right now, these are beyond the ability of applicators.
Parts must also be able to withstand the additional coating thickness of powder. Powder does go on heavier than typical paint.
The question keeps coming up about doing cylinders and cylinder heads. I have seen it done, but I would never do it to one of my own. I would STRONGLY advise NOT to coat these. You want to dissipate heat, not retain heat by putting an insulator over it! . Powder coating can be a great thermal and electrical insulator.
Colour and Gloss Choices
You can pretty much forget about truly custom colours per your specification. It simply costs too much to make a batch of powder for one application. Most coaters will have a good selection of "sample panels" from the powder manufacturers. There are some wild ones out there. A couple of years ago I did a bike "from the far East" with a Granite looking material that was a new sample from one of the manufacturers. The tank and fenders looked to be made of stone! It was very "Custom" looking and has become a standard material today. Gloss is measured as a percentage when viewed at a given degree. What this means theoretically is that 0% is like the inside of a camera, absolutely no reflection or gloss with 100% being like a mirror. For example, most gloss measurements are taken at a 60 degree angle. At this angle 35% would be a relatively low gloss and 90% would be a high gloss. The inside of a fairing is black and is low gloss so as not to reflect light toward the operator. We "keep the shinny side up" and that shiny side is is likely over 90% at 60 degrees. The other typical measuring angle is 85 degrees and that is used for lower gloss coatings. A gloss of 65% at 85 degrees is much less glossy than 65% at 60 degrees. The other factor that many consider is depth of image, which is a way to measure the ability of the finish to act as a mirror. Keep a few things in mind when you choose a colour and gloss. Very high gloss in dark colours are beautiful, but will show every fingerprint, not to mention bits of dirt. Besides being hard to keep clean, they are hard to apply. The slightest spec of dust in the air that lands on your part during curing will stick out like a sore thumb. This means that a quality coater will probably charge more for very high gloss, dark colours, or (worse), you will be disappointed.
There are some water clear clearcoat powders on the market now that can be topcoated over other liquid spray paints and powders adding to the look of gloss and depth. Say what you will about them, but look at the finish on a new Harley. All Harley tanks and fenders are wet spray painted and coated with a special clear powder. The look is stunning, you get amazing depth, but it is beyond the application ability of most coaters to apply successfully.
Orange Peel
Orange peel is a surface condition that looks just like it’s name, the bumpy skin of an orange. It is typical of some powders, and gets worse as the film thickness gets excessive. Most powders will apply at a range of 1.5-2.5 mils, which is thousandths of an inch in "coater language". When you start building heavier than this orange peel can be a definite problem.
Defects and Scratches
Polishing out Defects and Scratches Many small imperfections, minor orange peel, and some scratches can be polished out of a powder coated (or painted) product. The best material I have seen for this is 3M’s Finesse (sp?), available at most auto body supply stores.
Repairs
Once you have your precious parts powder coated, you will never be able to have repairs (chips, scratches, etc.) redone in powder, without tanking it apart, stripping and recoating. You can have a small touch up kit made by your local automotive paint supplier "made to match" as close as possible. Remember, special effect powders will not be able to be duplicated! To make life easier, I suggest having a 3"x5" or 4"x6" "Q" panel as they are called in the trade, or flat piece of metal coated at the same time as your parts. . Have the coater write the powder manufacturers company name, part number and colour name on the panel for future reference, (i.e. Morton, #PS2230, Ruby Red). Save this panel! Take it to an automotive paint tinter for a touch up kit. Many of them use colour computers today and this is the easiest way to get the match.
Powder Coating Myths
These came from threads I have saved from the bike lists.
"One of the nice things about powder is that it doesn't chip, it's plastic" - Partially True. Powder is a plastic, but so is ordinary paint. If done properly powder, is a little more chip resistant than typical auto re-paint paint, but it definitely can chip.
"powder coating simply cannot be made to last, it fades and peels off in a couple of years" - Not True. Many powder coatings are used in architectural structures and some are designed to last many years (20+) outside. The surface preparation and powder must be selected and applied carefully if longevity is a consideration, no different than liquid paint.
"Frames get dirty and are hard to polish up... the gloss sure fades under such conditions." - Not Necessarily. Fade comes from UV (sunlight) and is more a property of the type of resin used in a specific powder. Acrylics and TGIC Polyesters are some of the better UV resistant materials.
Listers Questions
Found your article most enlightening. A metallurgist friend told me a few years ago that things like aluminium wheel spindles should not be powder coated. He explained that aluminium billet material (6061-T6 ?) changed crystal structure at a critical temperature around 410 degrees F (as I recall). The thrust was that the heating step would adversely affect the strength of the material. Non-structural components would be OK, but not something that "holds the spokes on". The metallurgist is correct. Products like wheel billets, scuba tanks, etc. can be powder coated, but only with powders which cure below peak metal temperature of 300 degrees F. The crystalline realignment at 400 degrees F causes the previous ductile aluminium to become brittle. Imagine the catastrophe when an 80 cu. ft. scuba tank explodes under 3000 psi pressure after an unauthorised powder coat (this actually happened). To my knowledge, all Aluminium wheels and other strength-critical aluminium components are powder coated with these cooler curing powders.
I have an old BSA frame which over the years has suffered corrosion pitting in various areas. When I did the bike up I used filler in these areas and had the frame sprayed in cellulose, however I have found the finish to be excellent aesthetically but durability leaves a lot to be desired, can powder coated be filled prior to coating, if not to what degree does powder coatframes fill imperfections? Powder will fill minor imperfections such as some pitting from corrosion. It will probably do alright on a frame, as the round tubes hide more than a flat (say gas tank) would. I have never tried to use fillers with powder. From everything I know, they usually come loose on curing due to the different rates of thermal expansion from the plastic and the metal. Here is what I would do. I would try to find a piece of scrap metal that is corroded (approximately) the same as the frame. Clean it up by whatever method you would / did use on the frame, i.e. blasting, acid clean, etc. Take it to your coater and (if you can) have him coat it with the powder you are going to use, actually if it is a problem, almost any powder applied to a similar thickness will do. Then look at the piece, from the same distance that you would view your frame. This is important. The eye will not see nearly as many defects at arms length as close up. If the powder isn't good enough, use your filling method with a good 2 component spray liquid epoxy primer followed by a coat of 2 component spray liquid urethane.
"I have done some prep on some of the parts exposing bare metal ( I primered these parts afterwards). Will the primer hurt the powder coating process, will they have to sand blast off any primer I add?" If you feel the need to do some prep work first, and don’t know when you will get to coating, primer is not a bad way to inhibit rust until coated, but they can’t be reliably powder coated over the primer. If it were mine, I wouldn’t coat over any parts that came in primed, I’d blast it off. If you are going to blast off the primer, why do any prep?
"I'd like you to address an issue brought up in Jewell Hendrick's Superbike Tuning book in which he recommends realignment of the frame after powdercoating/heating. True? True only for really lightweight race bikes?" I don’t know for sure, but this is a possibility especially if the frame is "burned" prior to coating. It is another good reason to avoid that part of the process. Normal baking shouldn’t hurt but could conceivably relieve stresses from the welding process throwing it out of square. I have never heard of this happening, but it could.
"What parts are appropriate for powder coating,(i.e., should parts that get hot/cold be coated?" Use the same criteria you would for painting. If you would need heat resistant paint you would need heat resistant powder. There are some powders on the market (flat black) that are rated for 800°F continuos. I did see a set of Norton mufflers (NOT the head pipes!) that were powder coated with standard high gloss black that looked great.
"How about parts that might flex a bit?" Most powders have excellent flexibility unless put on too thick. I have seen many test panels that have been bent back and forth until the metal fatigues and breaks, with the powder fracturing only at the exact point of breakage. Poor performing materials will break and flake off quite a ways from the bend as stresses are put on the film.
"What is the best way to remove the powder coat without damaging the metal underneath? Are there different removal methods for steel or aluminium? The company I work for (as well as many others) make hot alkaline strippers for paint / powder that are used routinely for powder removal. We even have a hot stripper that takes paint and powder off of aluminium surfaces. Mechanical and burn methods are also regularly used to remove powder.
Listers Good Advice
"This item I learned the hard way. Make two lists of parts, with drawings if possible, and have the person who receives your work, initial both lists. Use this list to check that you get back what you gave them. Very important when small parts are involved. Also remember to take your list of parts with you and check together with the people who give you your parts back, that all your parts are there."
"When you go to pick your parts up, take boxes and protective blankets or towels. My service wrapped my parts in this Kraft wrap. Okay, but paper is known to scratch."
"Remember to check the quality of their work in direct sunlight, not interior light."
"The powder coat guy will not have the correct Whitworth fasteners for British bikes and may try to use incorrect threads, damaging yours and you may have to kill him later. This will seriously inhibit your restoration being in jail and all."
"My painter priced frame & swing arm together and all other part separately. Get this firmly in writing for the number of parts to be done by the firm you select."
"Your powder coater will charge you a pretty penny - insist on getting what you pay for. BTW, for any colour other than black, have them shoot a test piece first, lest you experience the intense disappointment I did about two weeks ago..."
"Use a powder coater who has a lot of experience with motorcycles. That rules out shops that mostly do lawn furniture and appliances."
"Let the shop do all the prep, that way they must be responsible for the final job and can't blame you for bad prep."
"If in doubt about the finish and colour, have them coat something very similar as a test and see how they do."
"Tell the coater what you want. He will be able to show you samples of his work."
"I asked my coater, I trusted them when they said, "Sure, that's what we do". My trust was well placed. If your guys are not so knowledgeable, you might ask someone who is."
"After I got the parts back, I ground off the powder coat in several places where there were electrical grounds to make sure I would have good electrical connections."
"I always let the powder coater clean and blast the frame. I have worked with industrial paint specs, and they always call for the primer to be applied within a few hours of blasting. Metal will start to oxidise immediately upon exposure to air! This also gives me an added benefit of a "single source of supply". By this I mean that the powder coater cannot absolve himself of responsibility for a bad job by blaming the Blaster."
"Tell the person who will spray your frame, to go light on the numbers area. I have heard too many stories of people who get their frame back and can barely read the numbers. You don't need headaches with the law."
The following list of powder coaters compiled from readers who have sent them to me, citing good experiences. This is in no way an endorsement by me. Insert all the usual disclaimers here!
U.S. East Coast
Essex Motorsports Connecticut "they duplicate the original Norton finishes. As they are a bike restoration shop first and foremost.."
Rainbow Powder Coating Company 498 E. Industry Ct Deer Park, NY 516-586-4019
Metal Refinishing Systems (aka Maryland Industrial Coatings) 5360 Enterprise Street Eldersburg, MD 21784 410/ 795-7130 ask for Darren. I stopped off this morning on the way to work to pick up my newly powder coated Commando frame. This is the third frame that the vendor coated for me, and they did their usual excellent job.
U.S. West Coast
Spectrum - San Francisco area: http://www.spectrumpowdercoat.com/
Craig Craft John McGeehan 14303 Lake Rd. Lynwood, WA 98037 (206) 743-4393 Fax: (206) 743-0231 "They powder coated a bunch of stuff on my /2 restoration, which later won a couple awards at the Washington State club's rally. They will do some small sandblasting, but prefer you to bring in your parts already prepped. The only problem I had was that some of the threaded holes needed to be chased afterwards. It cost me about $250 for the frame, swingarm, Earles forks and swingarm, 2 centerstands, and about 25 other pieces. Service was swift, I got all my pieces back the day after I dropped them off."
U.S. Midwest
Techno-Coat Inc. 861 East 40th Street, Holland, MI 49423 (616)396-6446 Ike Vande Wege, President. "Techno-Coat is a very high quality production powder coater. They are also rare in that they take in work from the public. They view this public work as their R&D area for looking at new coatings to take to their customers. An A1 coating house."
New Image Powder Coating 600 Spring Street Struthers, OH 44471 Jim Kolbrick (216) 755-1918 "this guy did an excellent job on my Commando, on time, and at the price he Quoted. He's near Youngstown OH."
Coating Specialties, Markham, Illinois. "Sorry, I lost their address and phone number. It is available from 708-555-1212. These guys specialize in motorcycle parts, and are excellent. They are used by at least 5 Harley shops in the Chicago area. Their work is first class, but they get backed up from Jan thru May (As one might expect!)."
SEALFAB, 1912 Columbus St., Two Rivers, WI 54241 920-793-5700 Tom or Brian Backler. Good quality house that also does impregnation on castings, i.e. that leaky porous engine case.
Trimen Ind. 925-B South Spring St. Port Washington, WI 53074 414-284-1816 414-284-1045 (fax) Ron White
U.S. South
Southern Powder Coating Inc. 2401 Georgia Highway Moultrie, GA 31768 912-985-2264
U.S. South West
Taint Paint 3368 Adobe Court Colorado Springs, CO 80907 (719) 447-9552 or 800-733-8374 "They did my 850 Commando frame and pieces, 2 colours for $190. Four other Brit bike riders in Colorado have also had their bikes done here, and all of us recommend this shop."
Sierra Powder Coating 1355 Industrial Way Sparks, NV 702 355-1075 "Real pros. Drop off your frame (mine had 5 pieces). Come back and pick it up with $125. Beautiful. All threaded holes had been plugged, as has the head bearing races, the serial number was easily readable. Included all prep work, and THEY masked the bearing races and plugged the threaded holes. A huge operation, and 100% professional."
Canada
ACS Coatings Inc. 1686 Dublin Ave. Winnipeg, Manitoba Canada R3H 1A8 Don Paszkowski 204-633-4755 204-633-4827 (fax)
Sun View Powder Coating Ltd. 18011 Bentley Road Box 605 Summerland, B.C. Canada, V0H 1Z0 Gord Cunningham 1-250-494-9222
Powder Blues Montreal Karry Gemmel 514-446-1876. "He's very familiar with bikes, has a 74 T150, some kind of Big Twin and a turbo kzxxxx or something, all are powder coated. I had the fender stays, battery box, both stands, footpegs and engine side plates done for about $100 Canadian, blasting included. He did the 2 torsion bars for my Avanti for $40. Typically his turnaround is a week for black stuff."
United Kingdom
Epoxy Powder Coating 215 Tyburn Road Birmingham B24 8BR (UK) 0121 328 2145
Martin Bell Stove Enamellers 6 Park Road , Hampton Hill, Middlesex TW12-1HD ( 020 8977-6122 )
Have a coater that you have had a good experience with? An error or typo? Please send all the information to me at davewrit@execpc.com and I will update the document.
To visit the Author Dave Wright's Home Pages
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