Greatings PSUBers,
I just got back from visiting a local boat dock fabrication company. They use the copper slag blasting media called Kleen Blast that I mentioned earlier, to sandblast all there steel weldments.
I got to feel the bare blasted steel that was blasted with the copper slag and it had allot rougher texture then steel blasted with 20/30 silica sand. It is also allot better for your health. This rougher texture makes primer, paint, and any other type of coating you would wish to use adhere to the steel better then steel blasted with silica sand.
After blasting the weldments, they are sprayed with a black Rhino Liner type material called Turbo Liner without any need for primer. Now remember these steel weldments are for docks that live just above the water outside, year round. Turbo Liner does come in a number of different colors as well. But it has to be sprayed by a very special machine that mixes the two parts at the gun, and has a heated hose. This material is dry to the touch in about ten seconds, just like the Rhino Liner brand.
They can spray it almost glass smooth, but they stand back and just mist the last coat of Turbo Liner to get the lite texture there customers want. You will see what I mean in my pictures on Frappr.
How well this sort of treatment on a weldment holds up underwater in fresh or saltwater without a primer, I'm going to find out. The guys at Rattleguard did a test on a large piece of wood, and coated it about 3/16" thick with there product and then put it in water for a couple of months. No water got through except in one corner where the coating was really thin. Of course this wood was not sent down deep but it can give you an idea. I'm still planning to use a high quality two part epoxy primer before I apply any other coatings, just to make sure. It will add some expense and time to any given project, but I would hate to try to remove any of these Rhino type coatings if I had rust starting to work under them.
I'm not sure yet how electrolyses will affect the steel when coved with a coating like this. I would like to know so I don't have to use zinc blocks if they are not needed. I've heard of allot of aluminum and steel boats being bottom coated with the Rhino liner and Rattleguard brands, but haven't been able to get a straight answer about corrosion issues, if any.
Best Regards,
Brent Hartwig