What the Specs Say...
According to the United States standards ASTM A 123 and A 767
(that are very similar to other global
galvanizing standards regarding coating
quality), require that the zinc coating have no bare spots and be free of blisters, flux spots, inclusions, and large dross inclusions. The same specifications also state that a matte gray finish is not in and of itself a cause for rejection. The matte gray finish is a sign of accelerated growth of the zinc-iron intermetallics due to steel with high levels of silicon. Cold-working may also result in this appearance. The ability of a galvanized coating to meet its primary objective of providing corrosion prevention should be the chief criteria in evaluating its overall appearance and in determining its suitability.
The galvanized coating must be continuous to provide optimum corrosion prevention. Handling techniques for galvanizing require the use of chain slings, wire racks, or other holding devices to lower material into the zinc bath. Chains, wires, and special fixtures used to handle pieces may leave a mark on the galvanized item. These marks are not necessarily detrimental to the coating and are not a cause for rejection, unless they have exposed the bare steel or created a handling hazard for erection personnel. If needed, these areas can be adequately repaired
by using an
acceptable repair compound.
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Visual Inspection Guide with Photos
