And here is what Diamond Seaglaze has to say about repairing areas of their doors and windows where the original powdercoating has been compromised. Also from the SENTOA website:
There are many varying opinions about what causes powder coat paint to fail, as well as what the best anti-corrosive coatings are to use. I have been heavily involved in the coating process and QA and NDT Testing on our powder coated and painted products over the years and am always willing to provide insight. First, I will address the repair question which was answered.
Most recoating does not require window/door removal, unless the problem has been left to fester for a great deal of time. Most corrosion manifests as the “bubbling” which was mentioned, and can usually be contained at that time for a relatively low cost. You need to get a two component urethane based marine grade paint, and primer. Depending on the suppliers in your area, you can often even get the paint in aerosol form, which is the easiest for re-application. We do not recommend the use on off the shelf spray paints, as it won’t stand up to the elements or have the same adhesion as this type. Our preferred paint suppliers are Alexseal and/or Awlgrip. Alexseal is ideal because the topcoat can be sanded and polished for a better blend, especially on the white colors.
Mask off the affected areas, and all parts that could be subjected to overspray. To achieve the best seal, cut away any sealants near the affected area(s) and clean it up with some isopropyl alcohol. Use a medium grit (80-120 grit) sandpaper to remove and condition the affected areas. If access is easy, an orbital sander makes the job go quickly. You will want to remove slightly more paint than the immediate area, as moisture may have seeped under the paint a bit. Once all damaged paint is out of the way, and you have everything masked, clean the area with water and a light detergent and allow the areas to dry.
Apply the primer to all exposed metal within 24 hours or preferably less. Lightly sand the primer after it has fully cured, as well as any areas that you will blend the paint into. It is possible to apply another coat of primer if needed, but it is not necessary in most cases. Finally, apply the topcoat, lightly blending into the original painted surface. Re apply if necessary. NOTE: The color may not appear to match right away. Let it cure fully, and then check it again. If it is off a shade, apply another coat of the topcoat, and allow to fully cure again. Once the painting is finished, un mask all areas and you are finished. Try not to rub or clean the newly painted areas for a couple days, as the paint takes a minimum of about 48+ hours to cure fully. (read spec sheet that you get with the paint for exact cure times)
The next question that was mentioned was what is the best coating for the marine environment. Well, anodized finish does not break down for a very long time, so I would rule this as the best way to avoid paint deterioration over time, but at the end of the day, most customers want matching “painted” products on their white Nordics. The best coating system is a wet paint primer/topcoat system. Our powder coat line is rugged and durable, but any location of any stainless steel fasteners that do not have isolation will eventually break down the surface of the paint and allow moisture in due to galvanic corrosion. Once this happens, the finish will deteriorate quickly. Powder coating provides a more durable, harder finish, but wet paint and gel coat are more flexible and easier to rework. Cor spec primers that are available with wet paint applications actually provide a sealed anti-corrosive barrier that protects the aluminum substrate much more effectively, and the topcoat is not the protective layer as is the case with power coat.
I agree, for the prep just make sure it is lightly sanded and wiped down with thinners before painting or the new paint will not adhere. If you are using a water based paint over oil based it will have to be primed but I would not expect you are using a water based paint.
