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 Rusting Stainless Steel		  New Topic  Topic Locked
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RoofRoof
Navigator

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USA
186 Posts
Initially Posted - 12/03/2002 :  16:38:40  Show Profile
I cut out a plate to cover a hole in the cockpit. The plate was stainless steel. After cutting with an angle grinder, I smoothed the edges with a brass wire brush on my bench grinder.

After only a couple days I started to see rust forming around the edges. Why? How can I stop rust from forming?
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Douglas
Master Marine Consultant

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1595 Posts
Response Posted - 12/03/2002 :  21:45:48  Show Profile  Visit Douglas's Homepage
Is it realy stainless. Test it with a magnet. The more the iron content the less stainless it is. I dont think you will ever find any true stainless. It all depends on quality or how it was manufactured.Stop it from rusting by painting it with a good epoxy.

Doug&Ruth
Triska (Alberg 29)
Tacoma Wa.
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JesseSmith
1st Mate

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USA
37 Posts
Response Posted - 12/04/2002 :  13:12:45  Show Profile
If you use epoxy on an exterior surface, make sure it have sufficient UV stabilizers. Epoxy will degrade in sunlight.
JS
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Dave Bristle
Master Marine Consultant

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Djibouti
10005 Posts
Response Posted - 12/05/2002 :  18:55:48  Show Profile
I'm going to go out on a limb and speculate that you're seeing galvanic corrosion from tiny particles of the brass brush in the tiny grooves and scratches along and close to the edge. I'd suggest smoothing with a stone wheel or other non-metallic abrasive and see what happens.

Incidentally, there's stainless and then there's stainless, identified by numbers such as 316 (generally better) and 304 (generally more prone to tarnishing). Usually what you see is not the kind of rust that structurally damages the steel--it's discoloration. Stainless steel prevents rust by creating a virtually invisible oxidation coating on itself. It requires oxygen to maintain that coating. However, dissimilar metals can affect that protection--you don't want to fasten stainless with bronze screws, for example.

Oops--I hear some cracking... I'm climbing back off the limb. <img src=icon_smile_blush.gif border=0 align=middle>

Dave Bristle - 1985 C-25 #5032 SR-FK-Dinette-Honda "Passage" in SW CT

Edited by - Dave Bristle on 12/05/2002 18:58:18
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Derek Crawford
Master Marine Consultant

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USA
3324 Posts
Response Posted - 12/05/2002 :  23:19:30  Show Profile
West Marine sells a pen-like product - you twist one end and glass fibres protrude from the other. It's designed to clean up hard to reach rusty areas - and it works well. (Expensive little job tho'!)
Derek
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Dave Seely
1st Mate

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46 Posts
Response Posted - 12/11/2002 :  13:58:34  Show Profile
If you are going to heat or weld stainless you have to be sure you get the low carbon stainless. 316L and 304L are what you need to look for. You created enough heat with the grinder to cause a chemical reaction where the chromium in the stainless reacts with the carbon creating chromium carbide. The free chromium will prevent rusting but the chromium carbide will not.
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Notice: The advice given on this site is based upon individual or quoted experience, yours may differ.
The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.