Cleaning and Degreasing before Powder Coating



cleaning parts powder coatingLets talk about the first step of the powder coating process. The very first thing to do is thoroughly clean and degrease your item. Even if it is brand new, it should be cleaned.After cleaning your part, check out this article for the following steps: "How to Prep for Powder Coating". The first thing you need to do is figure out what its made out of. Steel, aluminum, etc. Some metals like aluminum are very sensitive to certain cleaners and it can cause can corrosion and damage on a microscopic level. I will explain the steps I use to clean below.





Step 1. Pressure Wash



My very first step for any part that I am powder coating is to pressure wash the part. The pressure washer removes a lot of the loose debris like dirt and grease chunks with ease.  Pressuring washing can replace a lot of manual scrubbing and the part is usually clean the touch after. My pressure washer is not anything fancy, but it works great and has great pressure for a smaller unit. It is a 1900 psi electric model. I prefer the electric pressure washers because of how frequently I use it. If it was a gas powered pressure washer, I would have to start it up each time. If you are a powder coating small parts occasionally, an electric pressure washer is fine. Having a pressure washer is also extremely useful in every day life. It makes short work of cleaning anything that can handle the pressure.

Best electric pressure washer
cleaning parts before powder coating with pressure washer












As long as the part doesn't have any very delicate areas or is thin enough to bend, I set the pressure washer on the "pencil" setting. This focuses all the pressure into point and is very strong. I have actually managed to cut my skin with the water using this setting, so be careful. I just run this stream over the entire part until I no longer see the dirt coming off. I wear safety goggles while doing this because it splashes everywhere when hitting something irregularly shaped like a car part. If you really want to make short work of cleaning with the pressure washer, look at the gas-powered options. They are capable of a much higher pressures and can get your parts cleaner. Just be careful not to damage anything. This gas pressure washer puts out 2.5 gallons of water per minute. That's nearly double the electric pressure washer.




Step 2. Soak with Cleaner



How to Clean Aluminum Safely


Cast aluminum cleanerAfter the loose dirt and crud is off, I spray the part down with an aluminum safe cleaner. I am very selective about what I use to clean aluminum. A lot of normal household cleaners can corrode aluminum. After a lot of research on the right cleaner for aluminum, I decided on Simple Green Extreme: Aircraft and Precision Cleaner. It states all over the bottle that it was formulated specifically for aluminum and precision tools. I checked the MSDS and it is, in fact, not just relabeled simple green. After testing it out, I am very happy with it. Its not too expensive, but online is the only place I could find it. It cleans great. I also tested it by spraying on some scrap cast aluminum pieces I had, and just letting it sit for a couple of days. When I came back to the part and wiped off the cleaner, there was no signs of corrosion at all.

I used the simple green cleaner on this head. Unfortunately, I didn't get a good before picture, but in the picture, you can see the area I cleaned, vs the area I didn't clean yet. The 2nd picture shows it almost completely clean.

How to clean cast aluminum
Cleaning cast aluminum with Simple Green Extreme


How to clean cast aluminum
Head cleaned with Simple Green Extreme



How to Clean Steel & Iron


car parts cleaner Superclean
Cleaning ferrous metals such as iron or steel is a little more forgiving than cleaning aluminum. But there are some things to watch out for. You can use the Simple Green Extreme mentioned above with no problems. However, since steel can be cleaned with more easy to find and cheaper cleaners, I save the Simple Green Extreme for aluminum. For cleaning steel, I use a cleaner called Super Clean, formerly Castrol Super Clean which is amazing. Purple Power works okay too, just not quite as strong. I do not dilute the cleaner when using it on greasy iron or steel parts.






I did mention there are things that you have to watch out for with steel. What you need to watch out for is using any acid based cleaners on hardened steels. Most acidic household cleaners use weaker acids so it is not as big of an issue, but the chemical rust removers and things like that contain phosphoric acid or muriatic acid which can can cause something called Hydrogen Embitterment in hardened steel and even cast iron parts. Without getting to into it, basically hydrogen atoms can be absorbed into the steel, changing the internal structure which can lead the hardened steel part to break. This doesn't come up too much in the powder coating process but its something that's good to know. If I can help it, I don't use acid based cleaners on steel parts.



Step 3. Scrub



After spraying down the aluminum part with Simple Green Extreme or the iron/steel part with Super Clean, I let it soak for about 5 minutes, I spray a little more cleaner on the part and scrub it down with various nylon brushes. gun cleaning brushes are great for getting into bolt holes. A parts washer is a great place to do this task. Its the most convenient place to clean anything, it contains the mess, and constantly sprays cleaner out of the little nozzle. They come complete with a stand or you can get a bench-top model to save some space.

cleaning parts with parts wahser before powder coating

cleaning parts with parts wahser before powder coating










Step 4. Rinse & Repeat


After scrubbing the part thoroughly. I rinse it off with the pressure washer. I then repeat the scrubbing process and give it a very thorough final rinse with the pressure washer. I bring the part for a final rinse in hot water and then blow the part off with air to dry it.




Time Saver: Ultrasonic Cleaner


Another method I use for smaller parts, is an ultrasonic cleaner. I say smaller parts because the larger ultrasonic cleaners can be very expensive. They are coming down in price so I am looking into a bigger one. If the part fits in my ultrasonic cleaner, I will use it. Its a great way to outsource some labor. I use the same cleaning solutions inside the ultrasonic cleaner that I mentioned above. Although a very good ultrasonic cleaning solution recipe is 50% vinegar, 50% water, a couple drops of dawn dish soap and some baking soda. This solution will clean steel perfectly down to bare metal. It removes rust, zinc plating, and everything else. I don't bother making the solution because of the possible Hydrogen Embitterment issues(vinegar is an acid, although mild) and I just don't have a need for it anymore since I added the sandblasting cabinet to my garage, you may though...


ultrasonic cleaner for car partsThis my ultrasonic cleaner below. It also has a heating function which I'm sure does a good bit of the cleaning by itself. It works well for me, I use it for small parts and fasteners. I have cleaned heater cores, throttle bodies, brake master cylinders in it too, just have to flip the parts over to keep them submerged. It can clean where I can't reach with any brush. Sometimes I will think a part is clean, until I put it in the ultrasonic cleaner, and then the water starts to turn black. You can see the results below.



cleaning car parts in ultrasonic cleaner
Ultrasonic cleaner in progress.

cleaning car parts in ultrasonic cleaner
Fresh out of the Ultrasonic Cleaner.




Step 5. Bake / Outgas in the Oven

I then bake the part in the oven. This not only dries the metal completely from any moisture that may have been remaining, but it also outgasses the part. Cast aluminum and cast iron are porous. Grease, oils, and other impurities can soak into the metal over time. These impurities can also be in the part from the casting process itself. Outgassing the aluminum or iron consists of baking it at a slightly higher temperature and a little bit longer time than your cure schedule.


For example, say a powders cure schedule is 400 degrees for 10 minutes. I will outgas the aluminum at 425 degrees for 20 minutes. I do not start the 20 minute timer until the actual aluminum part is 425 degrees though. I check the temperature with a non-contact infrared thermometer. If you don't know why you should own an infrared thermometer while powder coating, read this article, they are essential for powder coating. For cast metal parts, you can actually see the part smoking in the oven, these are the oils evaporating out of the metal. If at 20 minutes, the part is still smoking, I will leave it in until the smoking is done and then an extra 5 minutes for good measure. I outgas every part I powder coat just to be thorough, but it is usually okay to only do it on cast items. I don't notice the extra oven use on my electric bill, but a powder coating shop that has large ovens would notice it.


The reason why you outgas a part before powder coating is to prevent it from happening during the curing stage. If those oils are left inside the cast aluminum, and you powder coat it and put it in the oven to cure, as the heat cures the powder, it also heats up the oils, causing them to expand. This expanding causes them to escape out of the part, leaving a nice pinhole in your powder coating finish which looks like:


Powder coating aluminum outgassing


Outgassing parts in the oven does solve about 90% of the outgassing problems when powder coating. However there are some parts out there that want to outgas no matter how long you bake it before hand. For parts like these, special powder coat primers and outgas forgiving powder coats need to be applied, but I will cover that a bit later.


Now that your part is clean, degreased, and outgassed. It is ready for media blasting (sand blasting). Stay tuned for the next post and leave a comment if you find the sight helpful.  For a thorough explanation of the remaining steps, head on over to "How to Prep for Powder Coating".

40 comments:

  1. Hey Sean- working on a set of motorcycle wheels that had stickers on them from the factory. I peeled & cleaned off the stickers just fine except for one. It left am impression in the aluminum some how and I can't get rid of it. Have you heard of anything like this? How do I get rid of it?
    Thanks.

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  2. Hey Lorin, When I I am dealing with an item that his stickers, my first step is to remove the sticker and then clean it really well with "Sticker and Label Remover." I do this first before the degreasing because the sticker remover itself is somewhat greasy. I have never had seen any remnants or outline of a sticker using this method I may be wrong here, but in your case, the sticker may have preserved the aluminum underneath of it while the rest was unprotected and oxidized. So what you are seeing isn't actually an imprint, but actually just fresh aluminum while the rest has aged. Follow my method for cleaning it up, and after sandblasting, the aluminum should have a completely uniform look and you shouldn't be able to tell there ever was a sticker. Thanks for reading the site, updates are slow at the moment but I will continue with new articles soon.

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  3. Hi, AMAZING amount of information you have put up here. Thank you! Wanted to let you know that the link to the parts washer is dead. I went ahead and located the new one in case you wanted to change the link. It's at:

    http://www.harborfreight.com/20-gallon-parts-washer-with-pump-60769.html

    Thanks again for sharing your knowledge and experience.

    Dan Hinkle

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    Replies
    1. Thanks for the positive words Dan, and thank you for noticing the dead link. I may be experience powder coating, but this is my first time running a website. I will make sure to go though the site from time to time and make sure all my links are still valid.

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  4. Great information thanks for sharing. I am restoring a set of aluminum wheels an have polished them and would like to preserve the shine by clear powder coating. Can I do a good degreasing, cleaning, rinse, off gas and then apply powder?

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    Replies
    1. That is interesting. I never thought about using an ultrasonic cleaner before, but I could see how it would be effective.

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  5. Yes, clear powder coating is great for protecting polished aluminum. Keep in mind that the powder coating will not adhere as well to a polished surface as it would to a media blasted surface, no type of coating does. However, it still does adhere and it should give you great results for a long time. Also the clear powder coat will slightly reduce the mirror look of the polished aluminum, just like almost all other coatings. Now that I covered the downsides, I will explain the process below.

    Step 1: Make sure the wheels are as polished as you want them. Once you powder coat the wheels, there is no going back and polishing them to a brighter shine.

    Step 2: Outgas the wheels. Bake the the wheels in the oven at around 425-450 degrees for at least 30 minutes. Start the 30 minute timer only after the aluminum reaches 425-450 degrees. If the wheels are still visibly smoking after 30 minutes, leave them in for longer until you see no more smoke.

    Step 3: You need to thoroughly clean the wheels of all polishing compounds and the cleaner used must not affect the shine of the wheels. Most cleaners will leave spots or hazing on polished aluminum. The cleaner that I use is MEK, it does not affect the shine and it does a good job of cleaning off the polishing compounds. It is a dangerous chemical so please read the MSDS and follow all the safety precautions (eye/face protection, chemical gloves, respirator).

    Step 4: After you believe the wheels are clean, perform the "Water break test". This is done by running water over the polished surface. The water should flow on the surface in a uniform sheet. Anywhere that you see the water bubble or split leaving a dry area, means there are still oils in that area. Clean the area again with MEK.

    Step 5: After you are positive all oils are removed from the wheels, they are ready to be powder coated. From the cleaning process to the powder coating process, do not handle the oils with your bare hands. Only clean gloves should touch the wheels.

    It sounds like a long process, but when it comes to powder coating polished aluminum, it is worth it to take the extra time for prep. There is nothing worse than having to strip the powder off and having to re-polish the wheels just because a little polishing compound was missed during the cleaning stage.

    Let me know if you have any other questions about coating the wheels,
    Sean

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  6. Good morning Sean for steel or iron recommend baking the piece before painting to degas.
    Greetings.

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    1. I would recommend pre-baking cast iron before powder coating as it can outgas. I have never had steel outgas on me so I would not say it is necessary.

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  7. Thanks. Lots of info there.
    I am new to powder coating and planing on coating a few sets of alot wheel.
    For the out gassing shold I be doing it before or after media blasting the old paint off.
    thanks.

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    Replies
    1. Clean first, then outgas, then sandblast.

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  8. what primers cover outgassing

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    1. They are usually called "outgas forgiving primers". Here is the one I use: Powder 365 Red Oxide (Outgas Forgiving) Primer

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  9. Thanks for the FANTASTIC post! This information is really good and thanks a ton for sharing it :-)
    Utah green cleaners

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  10. This is great advice for anyone interested in doing this at home. I have some steel structure out the back of my place that needs doing and i will give your methodology a shot. Thanks again.

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  11. Hello Great information. I want to powder coat my aluminum hubs But have heard that baking cast aluminum wheel hubs under high temps for long period can weeken the aluminum and cause hubs to fail and crack. What is your experience with cast aluminum? Should I outgas them for 20min then powder and bake. Can this weeken the hubs?

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    Replies
    1. I have never had an issue. As long as you keep your temperatures in check and aren't outgassing the aluminum at anything higher than 450 Degrees F, you should be absolutely fine. There are thousands of powder coated cast aluminum wheels out there and only a handful of examples of them breaking. I believe the scare has been blown out of proportion but that is just my personal experience. I outgas at less than 450 until I see they stop smoking and then give them a couple extra minutes.

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  12. Thanks for the awesome post! This information is really good and thanks a ton for sharing it :

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  13. Very useful information! I found a lot of helpful information, that I may need any time. Thanks for sharing

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  14. Great advice! Thanks for adding to the discussion.Thanks for putting this together! It looks very cool so far. I’ll be checking back to see the full plans.

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  15. Thank you Sean for your dedication and hard work. This has been a great read. Looking forward to more of your great info in the future.

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  16. Hi Sean, some great info so thanks for that. Have you ever clear powder coated polished cast iron? I've got an old cast window frame that I've polished and wire brushed and I'd love to keep the bare metal finish. There's bound to be some grease and dirt etc so I'm wondering how I'd go about cleaning it properly without causing it to start to rust afterwards. Also, would you expect the outgassing to result in it rusting as moisture etc is driven out? Thanks

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    1. I have clear coated bare steel with great results and as long as you achieve complete coverage, you should have no issues with rust for a long time. The best method would have been to clean it and outgas it first before using the wire brush to polish it. Outgassing it may cause some surface rust, however, this is not due to moisture, it is just a chemical reaction that iron experiences when in contact with air. Heat speeds up this reaction. So if you do decide to outgas it, be prepared to do a little refinishing.

      If you are just trying to clean it, I would use denatured alcohol on a clean rag and keep wiping it down until you are no longer seeing any residue on the rag. Denatured alcohol is not water based and therefore will induce rusting.

      Once you get to the final stages of cleaning it, only handle it with clean gloves, do not touch it with your fingers as the oils from your fingers can cause rust fingerprints to appear on the metal.

      After cleaning it, you should powder coat it as fast as possible. The denatured alcohol will remove any oils from the surface of the metal leaving it completely unprotected from rusting.

      I would do 2 coats of clear to ensure complete coverage.

      Hope that helps.

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    2. Amazing advice, thank you for taking the time to reply

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    3. Sean-

      Great stuff but I have a bit different problem. I bought some black powder coated wheels for my Jeep. I didn't care for the glossy look so I sprayed them with a satin clear coat. The clear coat dried hard and cracked. How can I remove the clear coat "paint" and not damage the powder coat below?? Thanks for your input!!

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    4. There are a couple of different things you can try and their effectiveness depends on how well the spray paint is adhered to the wheels. You can try mechanical removal such as an aggressive clay bar or rubbing compound. Neither of them should affect the powder coat but the clay bar is usually only for overspray, not an entire coat.

      Or you can try to chemically remove the spray paint. The issue with this is that there is a larger chance that powder coat will be affected. They won't remove the powder coat, but they can definitely affect the gloss black finish of the powder coat.

      Denatured alcohol is actually safe on powder coating and if the spray paint isn't that old, it should remove it with some scrubbing. This would be my first choice but I always have denatured alcohol on hand. Its sold at hardware stores such as home depot or lows.

      From there I would try lacquer thinner. This should easily remove the spray paint but it also has a chance of affecting the powder coated finish. If the other methods did not work, I would try this on the backs of the wheels and see if it affects the finish at all. If it is safe to proceed, then you can continue on to do the whole wheel. It may be best to do it in small areas at a time by applying the lacquer thinner to a rag. Do a small area to remove the spray paint, then immediately wash it and then continue on. If you start to see any black on your rag, then it is definitely affecting the powder coated finish and there is no reason to continue with lacquer thinner unless you don't care too much about the finish.

      I hope that helps. I have never had to remove spray paint from powder but these are the methods I would try, starting with the denatured alcohol first.

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  17. Sir how about galvanized iron sheet? What is the simplest and economical whay to prep for powder coating. Assuming that the sheet is new. I make enclosure boxes

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    1. Galvanized steel can be prone to outgassing during the bake cycle. This results in little pinholes in the powder coat from where the gasses escaped through the coating. This can usually be cured by outgassing the steel prior to powder coating. I usually outgass at 450 degrees F for 30 minutes to an hour or until the part has finished smoking. If the part still outgasses through the powder coating, you can use an outgas-forgiving primer prior to the color coat. This primer is applied to the part while the part is around 400 degrees and cures almost instantly. This product can be purchased from Powder365.com and it is labeled as red oxide primer.

      As far as preparing the galvanized sheeting, there is a process called brush blasting or sweep blasting that can be used to achieve some texture on the surface of the sheeting as well as remove any surface oxides. This can be done with a normal media blaster. The process consists of turning the pressure of the media blaster to around 40 psi and using a non-metallic abrasive. All of the blasting is done at no more than a 45 degree angle and the media blasting gun should be held about 15 inches away from the part. The main goal of this is not to remove the galvanizing so it must be done with a light touch.

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  18. Are you up for a new compressor and shopping around for a durable and affordable one? You should be able to research and learn about the different compressors out there before buying one so you can search.

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  19. Hi Sean,
    I love your site and it's very intersting too!!
    I work for a company that hasn't got any pre treatment plant. So we just wipe the items down with thinner and acetone. I would like to try to make a DIY tank where I could just dip items in maybe say 1.5M in length, is there anything you would recommend or is there any other way we could make it easier for our self. I can't seeing the company installing any pre treatment yet anyway.

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    Replies
    1. Thanks!
      First, I have to question the choice of acetone and thinner. It is not common, but acetone has been known to leave contaminants on parts. I would personally use denatured alcohol as a cleaning solution. As far as a tank, I'm not sure it would be the best bet for a cleaner as it would eventually accumulate oils and dirt which wouldn't make the best cleaning solution. However, I'm not sure of your exact procedures, so if you are looking for a tank, I would recommend a trough style tank so that it can accommodate longer parts. You can google trough along with your required dimensions and you'll hopefully find something your looking for.

      Another alternative is to simply spray on your cleaning solution nice and heavy and let it drip off of the part. This is commonly done by powder coaters using a commercial sprayer. Think of the backpack type sprayers but you don't actually have to wear it on your back. This method requires that you blow the part off with compressed air and to wait a little bit for the cleaner to completely evaporate.

      Hope that helps!

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  20. Completely prepared and skill in the field of cleaning, the expert cleaners give household and business cleaning as well as offer administrations, for example, cover cleaning and steam cover cleaning too. Every one of the administrations can be profited in focused costs and turned out to be at standard with the in house cleaner for household cleaning in the value of work they give. Quality Property Care

    ReplyDelete
  21. Sean - Not sure if you can suggest a cleaning product but here goes...I dripped a bit of spray foam onto an accessory that appears to be powder coated. Most of it came of with a razor edge but there is a small patch of polyurethane remaining. It's really bugging me and I don't want to make it worse...please help!
    Thanks,
    David

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    Replies
    1. That is tricky as everyone suggests acetone for removing spray foam. However, acetone will likely discolor powder coating so that would be a bad idea. I would start with denatured alcohol and see if it has any effect on the foam. If not, you can try goof-off or "sticker & label remover" (it should state that it is safe on painted surfaces). If none of those work, I am out of ideas.

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  22. Hi Sean,
    I'm interested in powder coating a motorcycle gas tank. What would you recommend to clean the inside of the tank so that it is safe to go thru the oven?

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    1. When I do motorcycle tanks, I fill them up with hot water and dawn dish soap and swish it around for a couple minutes, then i stick a hose in the tank and just let the water flush through the tank for 10 minutes. Then immediately blow out all of the water with compressed air. I haven't had an issue doing it this way.

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    2. Thanks Sean. I had been told I needed a special wash solution. Soap and water will be much easier. Appreciate the help!

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  23. I have had some wheels powder coated and have diamond cut them at work. I want to clear coat them after the diamond cut do I need to out gas them again or just a good clean then clear coat? Ok hanks.

    ReplyDelete