Offshoreonly.com - Paint stainless props to reduce galvanic corrosion?

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Paint stainless props to reduce galvanic corrosion?

I'm curious. I've done a lot of research on galvanic corrosion and am wondering if one could paint their stainless props to reduce it. I've never seen or heard of it being done.

The paint won't stick around long enough. If the boat never left the dock the paint would slow the activity.

Agreed, any paint that would be efficient enough would gas and peel too fast.

Hey Siearly, Are you in fresh or salt water? If you are in fresh sometimes you need to go with Magnesium instead of alum. It is much softer and works really well!

Quote:

Originally Posted by speedreeder (Post 2501282)

Hey Siearly, Are you in fresh or salt water? If you are in fresh sometimes you need to go with Magnesium instead of alum. It is much softer and works really well!

He means magnesium anodes (aka zincs) instead of aluminum. Also, you can get a prop zinc as well- this is required on Bravo 3 drives, and can be installed on Bravo 1 and 2 as well. Check out Boatzincs.com - its about $65 for a kit.

If you dont have them consider adding a merchathode system or make sure the one you have works.Also if you have shore power and use consider adding a galvanic isolator.

so what zincs for brackish water alum. or mag. ?

Brackish water should be aluminum. Only use magnesium in 100% fresh water.

Props are painted/ coated all the time - how many black aluminum props have you seen ? Paint is not smart enough to know the difference between Aluminum & stainless - Pre-treat the Ss prop with passivation or better yet with a blast profile of 1 - 1.5 mils in profile depth. Paint the props using epoxy. A Novalac epoxy or Cycloaliphatic Amine Epoxy will give you a good dense surface that will be most resistant to cavitation bubbles, however a simple polyamide epoxy will work well. With a blast prepared surface you can expect adhesion pull test numbers to be above 2,500 psi. Reducing the total amount of wetted SS surface will reduce the corrosion rate on exposed less noble metals. Even if you run the prop into a sand bar, not all the paint will come off and you will still have a lower corrosion rate of other metals because of the reduced exposed ss - Keep your dry film thickness low for best result - probably 3-4 mils. If you get lazy - an "epoxy powder coat" not polyester, will also work.