Galvanizers are required to have a bath of 98% pure zinc,according to the product specifications ASTM A123,A153, and A767, while the remaining 2% is comprisedof additives at the galvanizer’s discretion. One commonadditive is aluminum, which helps with the aesthetic ofthe coating. When excess aluminum is in the galvanizingbath, it creates black marks or bare spots on the surface ofthe steel (Figure 20). Bare spots due to excess aluminumin the bath may be repaired if only small areas are evident;however, if this condition occurs over the entire part, itmust be rejected, stripped, and regalvanized.
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