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Hot dip galvanizing - in contact with other metals

Use of hot-dip galvanized steel with structures made of other metals

The interaction of two dissimilar metals and the presence of electrolyte between them (e.g. water) may cause bimetallic corrosion. The effect can be reduced by isolating the two metals.

Copper and brass

Zinc corrosion is inevitable if contact between the two metals is not prevented. This can be done by insulating gaskets that are not conductors. Connect only with insulating fasteners and sealing sleeve.

Aluminum and stainless steel

In this combination, the problem of corrosion is extremely rare, except for too humid air, which can affect their interaction. In this case, electrical insulation is required.

Hot-dip galvanizing in contact with other metals

Stainless steel

From the very beginning of their interaction, zinc plays the role of the victim, until the steel does not have a protective layer of rust, which will serve as an insulating layer between them. This layer serves as a protection for the zinc coating. It prevents rust for many years.

Metal Exposure to the atmosphere Submerged state
  Rural Industrial Urban areas Coastal zone Fresh water Sea water
Aluminum А А-C А-C C C-C
Brass B B А-B B-C C-D
Bronze C C C-D B-C В-Г
Cast iron B B B-C B-C C-D
Copper B B-C B-C B-C C-D
Lead А А-C А-B А-C А-C
Stainless steel А-B А-B А-B B B-C

A Safe small effect of corrosion processes.

B Acceptable corrosion in some cases, little impact.

C — There is a need for additional protection, strong action.

D — Is a very strong corrosion resistance, to prevent the contact.

Guide to the use of galvanized metal with another.

a) Aluminium corrosion is unlikely but insulation is required due to the large surface area of aluminium.

b) Copper – requires electrical insulation of copper from galvanized steel parts, including in the atmosphere. It is necessary to avoid contact between water and copper, as copper particles can settle on the steel element.

c) Lead there are no problems with corrosion.

d) Stainless steel – usually small parts, such as washers or bolts, so the probability of corrosion is almost zero. Sometimes isolation may be required.

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