Re: Aluminum painting prep
Soda Ash (Baking Soda) blasting is the environmentally correct blasting method from what we are being told today.
BUT, if the boat has the factory paint on it, then you can save a lot of work and money by just cleaning it up with 220 sand paper and prime only the bare metal spots. The underlying paint, once scuffed will provide better adheasion than you are likely to achieve in a non professional environment. You do need to check for compatability issues.
Also, every paint manufacturer has their own recommendations as for prep. Some of it is very intesive and others fairly simple. It seems the more expensive the product the more intense the prep. Notice that I said more expensive but not necessarily better.
Bob likes the vinegar and water routine, I like a acid based prime wash like Interlux Viny-Lux. Both methods have their place and work well.