VMZINC in relation to other metals

Various metals can be classified in accordance with their reactivity potentials, relative to the normal hydrogen electrode.

If two metals are in contact, the metal with the higher potential in the electrochemical ranking decomposes the metal with the lower potential and, by accelerating corrosion, destroys it after a certain time.

In practical terms, a certain number of bimetal contacts are acceptable while others must be avoided. This is particularly important when installing lightning protection. In addition, water must never be allowed to run from a higher potential metal to a lower one: the water can contain charged ions which would accelerate the removal rate of the weaker metal.

Acceptable contact between alternative metals and zinc

Metals Comments
Lead There are no associated problems with this metal.
Aluminium Although a lower potential, it develops a passive layer on its surfacehas a similar protective coating, thus the two metals have very similar potentials, eliminating in building application conditions any the risk of corrosion.
Galvanized Steel Galvanization coats the steel with a thin film of zinc. This zinc-zinc contact poses no problems.
Stainless Steel Contact with Aaustenitic stainless steel and lead or tin-coated ferritic stainless steel is permissible.
 

Unacceptable contact metals

  • Copper.
  • Steel (Non galvanized).