firstly you etch, next you zinc-chromate prime(two-part)yellow,.then you two part any number of polyesters.......I recommend Smith & Co. in Point Richmond, California for the goodies! I''ve used MOST of his products in the last twenty five years as a boat repair Pro and they work!!For my profile and e-mail....maritimetradition.homestead.com
I''ve just had my 38'' all aluminium cutter done in the Bahamas and they used PolyButylZinc (which I think you are legally allowed to use if your boat is all Ali'') It cost me $1750. The previous job only lasted 22 months. More importantly - don''t drop any coins in the bildges or set up electrolytic actions. Expansion by request.
Don''t once it has the whitish oxidation it has its own coating. Some cruisers I know buffed it out once a year but what a waste of time. Lack of having to paint it is one of the beauties of owning a aluminum boat.
To dazeoff, have you ever seen with you own eyes a hole or any damage to a aluminum boat from coins in the bilge. Stray electic currents do cause damage but I have never seen "Coin" damage and would be interested in first hand accounts. The coin damage stories have been around at least the 30 years I have been in boating and I still haven''y seen it. Is this an old yachties tale?