Clean steel surfaces are an essential requirement for good hot dip galvanizing. Contamination in the form of grease, tar, paint and weld slag cannot be removed by chemical cleaning and may result in black bare spots after hot dip galvanizing. Specifiers should ensure that the fabricator takes responsibility for articles being delivered free from contamination.
Steel sections, which have been cut or drilled using suds type oil can give similar problems to burnt or anti-spatter sprays. The cutting fluid, which has been burnt or baked onto the steel, should be removed prior to sending the steelwork for galvanizing.
Contamination is sometimes difficult to detect on the steel surface and will only show up after the galvanizing treatment. The article may then have to be regalvanized, at additional cost.