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Bertram31.com General Bulletin Board
Re: Gas Tanks Again
Posted By: Peter In Response To: Gas Tanks Again (dave s)
Date: Friday, 23 June 2006, at 11:04 a.m.
Stainless steeel tanks are perfectly OK as long as you are not a charter boat. The Coasties in fact use sst tanks in some of their own boats.
The reason for not certifying them for use in charter applications is that there was/(is) concern about a type of corrosion called "crevice corrosion."
Crevice corrosion occurs when a microscopic sized crack fills with a corrosive agent like sea water before the protective chromium oxide film can form, and the corrosive agent remains there, blocking out the O2, and doing its damage over time.
This may have been a small concern before high-tech welding devices were widely available. Older style gas welds could contain imperfections, inclusions, and voids that would be sites for crevice corrosion to get a toe-hold.
I believe, as do many others, that this worry is all but eliminated with good welding equipment and technique. (TIG welding in particular) Still, you should be aware of the Coast Guard's official position.
The grade of stainless also makes a difference. You want something in the 3XX series, preferably 316L, which is highly corrosion resistant, and formulated to be welded. 4XX series is not as corrosion resistant, and some 4XX series stainless actually have magnetic properties that might effect your navigation equipment.
Personally, if it comes to it, I will go stainless for my own boat.
Aluminum is the a logical alternative, but Al has issues with being etched by ethanol. However, If you are a charter boat, this might be your better choice.
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