Slip Coated pre-galvanized Steel

A. Hi Harish.

Pre-galvanized means the material was galvanized in sheet form before fabrication. Therefore there will be no zinc at the sheared edges or the edges of holes, etc. If the item were post-galvanized, that would mean it was galvanized in its final fabricated shape.

Galvanizing can be done by hot-dipping (dipping the sheet or the finished item in molten zinc) or it can be done by electrogalvanizing (zinc electroplating the sheet or the finished item). Note that some people don't think that zinc plating should be called "galvanizing", but in your case ASTM A525 requires hot-dip galvanizing anyway. . ASTM A527 is/was a spec for galvanizing to "lock form quality"; I believe it was withdrawn in 1994 though, and replaced by ASTM A653.

A slip coat, to my limited understanding, is a water-soluble temporary coating that is put on the metal to discourage cargo like coal from sticking to it, by filling any small porosity, and by virtue of easily washing away (slip coat and tiny remnants together) after the cargo is unloaded.

Regards,