Zinc Alloys
Zinc can be deposited electrically with small amounts of
Cobalt, Nickel, Iron or Manganese to give increased
corrosion resistance above that of the pure zinc
coating. The solution has to be closely controlled to
ensure the correct concentration of alloying element in
the coating, otherwise the coating may be no better than
pure zinc.
                       
The alloy is able to reduce the rate of corrosion as the
electrode potential of the alloy under normal
atmospheric corrosion conditions is less than that of
pure zinc.

Zinc Iron  (Zincrolyte™)
This alloy is usually deposited from an alkaline
solution and should give a coating containing 0.3 to
0.7% of iron when the corrosion resistance of a
passivated surface is greatly enhanced, especially when
a black chromate is used.
the yellow type of chromate does not look very
attractive on zinc iron as it has a tendency to a
brownish colour. The black., however, gives in excess of
200 hours to white corrosion and with 8 microns can give
400 hours to rust in salt spray test (BS 7479).

Zinc Cobalt  (Zincrolyte™)
This alloy can be produced from acid and alkali
solutions, a cobalt content of 0.4 to 1.0% being
required to give enhanced corrosion resistance. The
chromate passivate coating is similar to that of zinc
with a higher iriddescent by a higher cobalt content
and it is possible to produce a good black passivate on
jigged components. Ronde BV is a major supplier of
barrel and rack plated parts in this finish.

Testing
It is important that all alloy coatings are supplied
with the correct amount of alloying metal, which can now
be tested non-destructively using X-ray fluorescence
techniques.                         

Different articles with Zincrolyte™