Alminum and Stainless compatibility

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I am repairing the transom on an aluminum boat 5086 H-116. I am wanting to take the wood out and build a stainless 316 square tube frame and put in its place sandwiched between two pieces of aluminum.Will this cause the aluminum to corrode too much?
Reply:Yes, that would be a bad combination for galvanic corrosion.http://www.ceoe.udel.edu/seagrant/pu...corrosion.htmlhttp://corrosion-doctors.org/Definit...nic-series.htmFound via searching on Google with the words 'metal galvanic corrosion'.  Google says it took 0.43 seconds to return 209,000 'hits' on that search.  You -do- know about Google, right?    The best laid schemes ... Gang oft agley ...
Reply:I did do a Google search but thought that because that part wasn't submerged it might not corrode as bad. The stainless material I have was free and seemed like a better idea than going back with wood I have seen this done with aluminum channel I will go buy some.Thanks for the reply.
Reply:Stainless steel fasteners are routinely used with aluminum boats, so the galvanic corrosion between aluminum and stainless cannot be too big a problem.http://forums.iboats.com/showthread.php?t=59334That said, a lot depends on the exact exposure.  If both the aluminum and the stainless will be underwater, that is probably more of a concern.  But then, any metal boat should have a sacrificial anode to protect the hull and hardware.If the stainless and aluminum will generally be in a dry or semi-dry situation, the galvanic corrosion will be less of an issue.From your description, I can't quite imagine the degree of exposure to water.Of course, salt water is more corrosive than fresh water.One other issue is the coefficient of thermal expansion.  The difference between Stainless and Aluminum is large enough to cause problems, if you don't allow for it.  If you use mechanical fasteners, a slighly larger hole could allow relative movement, and minimize that concern.The other concern that I would have about laminating stainless between aluminum sheets is the inability to inspect for problems.  If it was out in the open it would be more likely to dry out, and easier to find problems if they do occur.Sculptures in copper and other metalshttp://www.fergusonsculpture.comSyncrowave 200 Millermatic 211Readywelder spoolgunHypertherm 600 plasma cutterThermal Arc GMS300 Victor OA torchHomemade Blacksmith propane forge
Reply:Stainless fasteners are routinely used on aluminum boats without problems, so galvanic corrosion cannot be a big issue.http://forums.iboats.com/showthread.php?t=59334Coefficient of thermal expansion differences could be an issue, but if you use mechanical fasteners, and have a little slop in the holes, that should be ok.I could not tell the exact exposure of the stainless/aluminum, whether it would be dry, wet, semi-dry, etc.  Obviously fully wet would be worse.I did not see if you were in salt water or fresh water, that makes a difference.The other issue is laminating stainless between aluminum, in that you might not be able to inspect the joint.  Always best to design in inspectablity, especially if there is any possibility of problems.RichardSculptures in copper and other metalshttp://www.fergusonsculpture.comSyncrowave 200 Millermatic 211Readywelder spoolgunHypertherm 600 plasma cutterThermal Arc GMS300 Victor OA torchHomemade Blacksmith propane forge
Reply:how will the ally be fixed to the stainlessBOILERMAKER
Reply:I have decided to go with a pourable product called Seacast instead of the metal or wood no worries that way. The stainless probably would last a while it would only be wet if the boat filled with water. Thanks for the help! Attached Images