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Galvanic Compatibility Corrosion Guide
Dissimilar Metal Corrosion Guide

Corrosion / Galvanic Compatibility Table of Contents
Metal Products Supplier
Engineering Metals and Materials Table of Contents

Galvanic and Corrosion Compatibility Dissimilar Metal Corrosion Guide

Quality engineering and design requires an understanding of material compatibility. Galvanic corrosion (some times called dissimilar metal corrosion) is the process by which the materials in contact with each other oxidizes or corrodes. There are three conditions that must exist for galvanic corrosion to occur. First there must be two electrochemically dissimilar metals present. Second, there must be an electrically conductive path between the two metals. And third, there must be a conductive path for the metal ions to move from the more anodic metal to the more cathodic metal. If any one of these three conditions does not exist, galvanic corrosion will not occur.  Often when design requires that dissimilar metals come in contact, the galvanic compatibility is managed by finishes and plating.  The finishing and plating selected facilitate the dissimilar materials being in contact and protect the base materials from corrosion.

For harsh environments, such as outdoors,  high humidity, and salt environments fall into this category. Typically there should be not more than 0.15 V difference in the "Anodic Index". For example; gold silver would have a difference of 0.15V being acceptable.

For normal environments, such as storage in warehouses or non-temperature and humidity controlled environments. Typically there should not be more than 0.25 V difference in the "Anodic Index".

For controlled environments, such that are temperature and humidity controlled, 0.50 V can be tolerated. Caution should be maintained when deciding for this application as humidity and temperature do vary from regions

Gold, solid and plated, Gold-platinum alloy
Rhodium plated on silver-plated copper
Silver, solid or plated; monel metal. High nickel-copper alloys
Nickel, solid or plated, titanium an s alloys, Monel
Copper, solid or plated; low brasses or bronzes; silver solder; German silvery high copper-nickel alloys; nickel-chromium alloys
Brass and bronzes
High brasses and bronzes
18% chromium type corrosion-resistant steels
Chromium plated; tin plated; 12% chromium type corrosion-resistant steels
Tin-plate; tin-lead solder
Lead, solid or plated; high lead alloys
Aluminum, wrought alloys of the 2000 Series
Iron, wrought, gray or malleable, plain carbon and low alloy steels
Aluminum, wrought alloys other than 2000 Series aluminum, cast alloys of the silicon type
Aluminum, cast alloys other than silicon type, cadmium, plated and chromate
Hot-dip-zinc plate; galvanized steel
Zinc, wrought; zinc-base die-casting alloys; zinc plated
Magnesium & magnesium-base alloys, cast or wrought

Other documents of interest:

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