Priming bare metal spots below water line.

[Oceanride007]

Have a 40ft Mono steel, my method is wrong because It tends to polish the hull with Scotch brite, or wire brushing, or Oxylic acid, then have trouble with first coat sticking properly, use angle grinder with course grit is no good because it'll burn the metal causing much the same problem, was thinking of a product on chandlers shelf called Norglass Metal etch Gel but its made of phophoric acid same as my Oxylic acid.
Trying to avoid Grit blasting.
Any suggestions.

[SailingHarmonie]

Originally Posted by Oceanride007

Have a 40ft Mono steel, my method is wrong because It tends to polish the hull with Scotch brite, or wire brushing, or Oxylic acid, then have trouble with first coat sticking properly, use angle grinder with course grit is no good because it'll burn the metal causing much the same problem, was thinking of a product on chandlers shelf called Norglass Metal etch Gel but its made of phophoric acid same as my Oxylic acid.
Trying to avoid Grit blasting.
Any suggestions.

What product are you using as a primer? That’s kind of important to know, don’t you think? My advice would be to follow the advice from the manufacturer of that product EXACTLY.

And just so you know, oxalic acid and phosphoric acid are not at all the same thing. Throwing random techniques and products at the problem is never a good plan.

[Wotname]

Norglass Metal etch Gel is not suitable for steel (above or below below the water line). It is an etch cleaner for non ferrous metal. Yes, it will treat rust (like most rust converters) but it doesn't remove rust, rather it just converts it from iron oxide (rust) to iron phosphate (an inert stable compound). Totally unsuitable below the waterline.

It you want to use a Norglass product, the only suitable one for steel below the water line is Norshield Anti-Corrosive Primer. https://norglass.com.au/products/pri...rrosive-primer

Grind the spot back to clean bare steel using a standard steel grinding disc, give it a quick power sand with a new sharp sanding disc (say 80 or 120 grit) and apply primer without delay. This method goes for almost any steel primer if you can't grit blast.

FWIW, I have had good results with other Norglass products but I have not used the above primer.