316L SS, Al fittings and saltwater

[brgriffi]

Hello,

We're having an issue with galvanic corrosion for some of our products installed in locations exposed to salt water. We have large grates made from 316L SS. Attached to these grates is an aluminum (part 2024, part 6061) hose fitting and braided SS hose.

We had installed electroless nickle-plated aluminum fittings, but these have corroded and failed in less than a month at one particular location. We can also get this same fitting with a Type II anodization, but we are concerned about galvanic corrosion between the aluminum and SS. The amount of SS is very large compared to the amount of aluminum on a typical installation. I've attached a rendering of one of our installations.

Would the anodized aluminum be a good option, or do we need to look into other options that will allow us to get a stainless steel fitting?

Any help or advice would be greatly appreciated!

Thank you,
Brandon

 

[MikeHalloran]

There are two possible defenses:
- ALL stainless.
- Stainless and aluminum pieces galvanically isolated by plastic bushings, spacers, etc., typically at least 2mm thick. Anodic coating would theoretically work for this purpose, but it's easily breached and rather thin, so easily bridged by a drop of salt water.







Mike Halloran
Pembroke Pines, FL, USA

 

[EdStainless]

All will be the only reliable solution. The potential difference is so great that a coating would have to be very good. A few mm of 100% solids epoxy might work.

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Plymouth Tube

 

[CoryPad]

The oxide layer on anodized aluminum is porous and must be sealed for improved corrosion resistance. Even then, the performance is not likely to be good. Go for stainless.

 

[brgriffi]

Thank you for the responses, everyone. We're tracking down a new supplier who can get us stainless fittings.