This is the question you might be asking. See here and here for previous references; I’m sure I have piqued your interest. (I had never asked this question before buying a steel boat simply because I had never heard of Ospho. It’s not something that comes up as a topic of conversation in the circles I run in. So…you’re welcome for broadening your horizons.)
Ospho, for those who are just dying to know, is a rust converter. It converts iron oxide into iron phosphate. At least that’s what it claims. I know that a large bottle of it came with the boat, that it smells like Death’s ass, and it turns rusty steel black.
There are two distinct camps when it comes to Ospho. There’s the It Will Never Work So Save Your Time And Your Money And Just Do It Right In the First Place camp. Then there’s the We Are Doing The Best We Can With What We Have camp. We are in the second one (surprise, surprise).
After chipping the rust off as best we could I went around with a foam paint brush and dabbed this stuff on the chipped areas. It has the viscosity of water and is easy to spread.
After a few minutes the vaguely rusty steel (because it’s impossible to get all the rust off with a chisel) starts to turn black.
As a matter of fact the bottle recommends that some of the light rust be left on the surface of the steel so that the Ospho has something to “work with”. At least, that’s what I think it says because the bottle we have is not in the best shape and the printed instructions are a little blurry.
Anywhoo, we were mightily heartened by seeing this transformation and felt that a beautiful, bristol-condition yacht was surely just a few days away.