Originally Posted by
Korina
Not a badly designed experiment, especially for "home grown."
However, one thing should be clear: Very few surface treatments, of any kind, will permanently prevent corrosion. Once it starts, corrosion tends to work under any coating or treatment. Phosphatizing alone is probably one of the best, phosphatizing under a good paint is better. Powder coating hasn't been around long enough to be sure, but it looks good too. The reason I recommend a coating that incorporates zinc phosphate is that I helped develop one of the few paints that would actually prevent rust from spreading once initiated. It was an epoxy-resin-zinc phosphate brushed or aerosol applied paint. It had incredible durability and adhesion, too. Unfortunately the company is no longer in business, though the formula may have been acquired or imitated by another coatings manufacturer. I recommend investigating automotive coatings, as some of them do an incredible job, particularly those used on Volvo, Saab, BMW, and possibly Toyota and Honda. Coatings technology is always changing and growing. What was "best" yesterday has probably been surpassed today.