Any Problem using Copper paint on stainless steel

[ras737]

Just purchased 4 gallons of Pettit Hydrocoat. Can I use this on my stainless steel hydraulic platform? I know they make an eco formula that's made for metal, but is it necessary? I have been using this for years on my trim tabs and I never noticed any galvanic corrosion. As everyone knows this stuff is not cheap and I would prefer to use what I have if possible. Thx

 

[hughespat57]

I'm going to refer you to two good sources on this. But first and foremost you should not if possible.
I know even 316L Marine "Stainless Steel" will start to bleed a little rust color. And growth or barnacles may be your concern not looks. But stainless needs oxygen, otherwise if you seal in any moisture you will get "crevice corrosion" pitting and weakening of the enclosed portion. With bolts when this occurs it may not even be noticed until the bolt is removed or worse fails in the center.

If you paint stainless there are no shortcuts, prep, prep and be sure to prep. It is a multi-layer process to get a good adhesion and good results. In the end the copper won't be a concern because you will have three layers of wash, prime, coating under the bottom paint.

https://www.pfonline.com/articles/painting-316l-marine-grade-stainless-steel
https://www.powerandmotoryacht.com/maintenance/painting-underwater-metal

 

[Blueone]

Call the manufacturer...they have very good customer service

 

[Henry Boyd]

Patrick is correct, all commercial grade stainless when constantly submerged will oxidize and blush, and that includes even Mercury Bravo 3 props.

I am refinishing the pods and props on our boat this year and consulted both Volvo and Pettit. Volvo recommended an epoxy primer and non copper anti fouling top coat on the pods and prop specific anti-fouling , but not a specific brand. Having had good experience with Pettit products, I consulted them for their recommendation. Their suggestion: 4700/4701 epoxy primer and ECO HRT for the pods and Prop Coat for the props. Although our underwater metal is NiBrAl, the protocol is the same with the only variable being the use of a base metal specific primer.

Keep in mind this type of system is two part. The epoxy forms a barrier layer that acts as electrical insulation to reduce galvanic corrosion. The anti-fouling keeps down the marine life growth.

Copper laden bottom paint will have an effect on stainless steel by accelerating galvanic corrosion. How bad it would be, and could it be worse than bare stainless are questions we can’t answer.

if you must use anti fouling, the best course would be to use one intended for use on metal.

 

[ras737]

Some really good info here. Thanks I appreciate the help.