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galvanic protection for stainless steel/zinc contact

galvanic protection for stainless steel/zinc contact

galvanic protection for stainless steel/zinc contact

(OP)
Hello,
I am a conservator of outdoor sculpture restoring a cast zinc monument appoximately 15 feet tall that was severely damaged when hit by a falling tree.  Although I can restore the zinc skin through re-soldering the shattered pieces and replacement castings, I wish to install a stainless steel amature to carry the weight of the assemblies without relying on the zinc which was originally un-reinforced.  When I have done this in the past I used neoprene pads, teflon bushing and zinc rivets to connect the two but, although efective at avoiding contact between metals, it allowed too much movement for this installation.  Does anyone have experience in hot-dip galvanizing of stainless steel?  I thought I might use it not as a sacraficial coating but rather as a buffer between the zinc skin and the ss structure.  Any thoughts, better ideas?

Thanks a lot

RE: galvanic protection for stainless steel/zinc contact

Hot dip galvanizing of stainless is rare because it's kind of a material oxymoron, but it can be done. Stainless is commonly terne coated ( lead-tin alloy ) for roofing. It is seldom coated, not because it can't be, but because it is generally unnecessary.
 Are you sure galvanic corrosion will be a problem? If the stainless is not exposed to the environment, you may not have the required immersion of the joined metals in the same electrolyte.

RE: galvanic protection for stainless steel/zinc contact

(OP)
Thanks for your thoughts.  I remember now that you mentioned it that ss is provided tern coated for roofing.  I have reanalysed the situation since the post and thought, as you said, that the likelihood that the metals will be within an electrolitic condition is remote.  The original bolts used in the installation were brass and there was no evidence of corrosion at any of the assembly points.  I have reduced the contact points by isolating as many assembly points with ss clamps pressure fit to the zinc and isolated with rubber washers.  At the few points where the ss and zinc will be in contact I am using brass bolts as per the original and attempting to maintain a dry environment by sealing the joints.

Thanks again.

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