Home/Sitemap  ·   Search  ·   you are here: Forum =>letter 2404 Galvanic action between Aluminum & Stainless Steel -- I have a client contemplating thermal sprayed aluminium to his traveling screens at a power station. Would there be a galvanic or sacrificial action where aluminum is in contact with stainless steel in a wet environment? Greg N thermal spray - Victoria, Australia -- Aluminum and stainless steel are far apart enough in EMF to cause significant corrosion in a moist salt water environment. An alternate that might work is nickelaluminide. I really like the metallographic results from a small system from TAFA. Beautiful laminar coating. virtually no porosity. It is a dual wire system. Miller has a big one but is too big for most work unless you are doing aircraft carrier antiskid on the decks. I would try one and see how it worked. If it worked OK for several weeks, do them all. James Watts - Navarre, Florida -- I was wondering if you could describe in 50-100 words galvanic action in metals, in general terms. I'm currently studying and cannot find any info describing what takes place in this process. Much appreciated, Thank you. Christopher C - Gold Coast, Q,ld, Australia Sure, Christopher. Picture a dry cell battery. It provides electricity and eventually it will eventually run down. The battery consists of two different metals: the shell including the negative pole is made of one metal. The rod is made of a different metal and is attached to the positive pole In between the rod and the shell is a conductive gel or glop. For the battery to provide electricity (for you to use it), you have to connect wires that provide a metallic path from negative to positive that electrons can follow. So, what happens is positively charged ions of metal dissolve into solution from the positive pole and migrate through the glop and reach the shell. Meanwhile (if the battery powered device is turned on), electrons travel through the wire from the negative pole to the positive. The positively charged ions meet the electrons, which reduce the metal back to metallic state. At some point all the metal from the rod dissolves, or the shell gets completely coated with metal from the rod, so there is now only one metal exposed instead of two, and the battery is "dead". Dissimilar metals in a device can comprise a battery whether we want them to or not. If you have two different metals, and they are sitting in salt water or another conductor, you've got a battery. If you now provide a metallic path between the two metals (either a piece of wire or just bolting them together), the battery is "running", i.e., one of the metals is corroding. Ted Mooney, P.E. finishing.com Brick, New Jersey

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