I have been a lurker for a while but have some info as I work for a company which produces powder coating powder so have some experience:
• There are multiple types of powder coatings available on the market much in the same way you can get water based paint that your kids use through to ultra high temperature paint used on the insides of ovens. The same product may even be coated with different types of powder over the years so each situation can be different.
• The market place and its needs have changed dramatically over the past 5-10 years. This means that where as 99% of powder coatings 10 -15 years ago where generally resistant to most domestic chemicals ( petrol , diesel, cleaning fluids) and had good UV and environmental resistance (5-10 year life span typical). Now a days powders are designed for certain uses and useless for most others, unfortunately a lot of coaters just go for the colour and texture and forget about the end use or the customer just asks for the cheapest.
1. To remove powder coating “domestically” you can split them into 2 groups : Reactive or unreactive.
a. Reactive coatings will react when they are first applied and form a chemical and temperature resistant form. Identify by scratching the surface then hold a heat source very close by if it does nothing then starts to burn or char it’s a reactive.
b. Unreactive coating these are just melted to form the coating. Identify as above but this type will “self cure” as the edges of the scratch start to soften and the scratch heals.
2. Once you have identified the coating type:
a. Reactive types. These need to be destroyed / removed by mechanical means or by extreme temperature or extreme chemical attack. Your line of attack should be
i. Flame the surface until it chars DO NOT SET light to the product as that just gets messy/ dangerous ( fumes).
ii. Mechanically remove, best bet is blasting using which ever media is the cheapest media available as this will become contaminated for future use. Wire brush / scrappers can be used but 80% of powder coatings now have adhesion promoters which means the product will not peel off rather chip of.
iii. After a first pass or when you can see more of the original colour / texture rather than a burnt surface reuse a flame to char the ruminants so you are always removing burnt material.
b. Unreactive types. These are more of a pain as when they get hot they melt so will contaminate / get every where.
i. Ideal way, get it in the freezer for at least 4hrs. Then mechanically remove, blasting is the industrial way but the best DIY is to scrape / chip or use a hot air gun that can be controlled so you only heat the area you are going to scrape off.
ii. Burn the lot off, this is not ideal as its dangerous for the part (distortion), you ( fumes) and very messy. Also as mentioned above most coatings have adhesion promoters which leach into the substrate, these have the action when burnt of contaminating the surface of the part for a few micron which means subsequent coatings can be ****.
iii. Chemical attack – least favoured but for DIY use may be best as it comes in cans and needs nothing more than a brush, safety equipment lots of time all of which are readily available for the DIY’er. You must take precautions as you want to remove the coating in layers constantly scrapping of the reacted surface and then reapply to the fresh surface underneath. STOP before you get down to bare metal as most of the chemical agents love to react with the metal below which causes nightmare for subsequent coatings. But if you sit there watching, scrapping then reapplying you can get good results at home. As for which chemicals are best I have no idea as I am based in the UK and we use pure chemical rather than branded mixtures. As with point 1 above one persons results may not be the same as yours its **** it and see.
As for the nay sayers “ it falls off”, “ it chips and then rusts under neath” yes it did but times move on and the latest generations of powder coatings have there place as long as they are chosen correct based on the end use.
So you would much rather have a coating that comes off with your fingernail or flakes off when you spill something on it?
And a couple of you have friend requests coming.