I've seen a few references to anodized stainless steel in this thread and others about water heaters on the forum.
I am very far from a chemist or metallurgist. I don't really understand how a ferrous metal can be anodized. Or, why one wants to anodize stainless steel, if one can.
What is the anode oxide? I thought stainless steel worked by forming a very thin protective surface layer of chromium oxide which to my knowledge isnt an anode. And that, additionally, some grades of stainless are alloyed with a small amount of moly to strengthen the austenitic matrix, making oxidative corrosion dramatically harder.
The upshot being that stainless steel doesn't need a sacrificial coating and that as long as there is oxygen in the water and it isnt crazy acidic the oxide coating is self repairing until it pits badly enough to not get oxygen.
It would seem to me that anodizing stainless steel would require some plating or vapor coating of aluminum or magnesium or some other sacrificial metal to subsequently be chemically oxidized. Or something.
And, that sounds more expensive than a good stainless, the point of which I thought to be that it is protected by relatively inert and self-repairing chromium oxide and, beyond that has a strong, hard to oxidize matrix.
I known that if flow rates arent consistently high enough, as is probably the case in many boats, sulfur-reducing bacteria can get a foothold and speed corrosion of lower grades of stainless -- but I thought preventing this was the point of the moly in superaustenitic 316 stainless steel.
What am I missing?
Many thanks!
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The key word you used is "theoretically".
Stainless steel is not all the same. Is it 304 or 316 stainless?
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It should last much longer than glass lined but still not forever.
If you can afford it, for longevity, I would eliminate as much steel or galvanized steel as possible.
Good luck on your project!
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