Unistrut International 16100 S. Lathrop Ave. Harvey, IL 60426

Phone: 708-339-1610 800-882-5543 Fax: 708-339-7814

www.unistrut.com

GALVANIC CORROSION

Galvanic corrosion occurs when two Corroded End dissimilar metals are in contact in the (Anodic, Least Noble) presence of an electrolyte, which is a medium through which an electrical current Magnesium can flow (i.e. moisture). The rate of Magnesium Alloys corrosion depends upon the amount and Zinc concentration of the electrolyte as well as Aluminum 1100 the difference in electrical potential (anodic- Cadmium cathodic relationship) of the metals as Aluminum 2024-T4 shown in Galvanic Series Chart to the right. Steel or Iron Cast Iron A highly anodic material in contact with a Chromium-Iron (active) highly cathodic material will corrode much Ni-Resist Cast Iron more quickly than two highly cathodic Type 304 Stainless (active) materials or when the materials used are Type 316 Stainless (active) closer together in the Galvanic Series Lead-Tin Solders Chart. Lead Tin When corrosion does occur, the anodic Nickel (active) material is the most likely to corrode, Inconel Nickel-Chromium Alloy (active) whereas the cathodic material is the least Hastelloy Alloy C (active) likely to corrode. Brasses Copper To reduce the likelihood of galvanic Bronzes corrosion in a fastened joint, it’s Copper-Nickel Alloy recommended to choose materials that are Monel Nickel-Copper Alloy grouped together in the Galvanic Series Silver Solder Chart. If that’s not possible, other Nickel (passive) recommendations are: Inconel Nickel-Chromium Alloy (passive) Chromium-Iron (passive) 1) Select materials that are as close Type 304 Stainless Steel (passive) together as possible in the Galvanic Type 316 Stainless Steel (passive) Series Chart Hastelloy Alloy C (passive) 2) Provide a barrier between the two Silver metals, such as paint, non-metallic Titanium washer or gaskets Graphite Gold 3) Design the fastener as the cathode so Platinum the cathodic area is small as compared

to the anodic area Protected End 4) Use a metallic finish on the fastener (Cathodic, Most Noble) that is close on the chart to the mating material