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galvanized coatings



This response came from the National Metal Finishing Resource Center
On-Line Conference:

Some galvanizers add lead to their galvanizing pot for a number of
reasons, including making it easier to fish out dropped parts which will
float on the surface of the lead (the lead sits on the bottom of the pot
below the zinc) and to improve fluidity of the zinc.  Other galvanizers
add different metals including nickel to improve the properties of the
galvanized coating. 

About 1% lead is soluble in solid zinc and a large amount of this lead
seems to congregate in the surface layers of the coating -various
electron micrographs bear this out. 

When the galvanized item is cleaned and etched, the lead or nickel is
passed into the cleaner, the rinses and the etch solution so that the
heavy metal "impurity" will eventually find its way into the waste water
stream. 

Hope this helps. 

Mario Pennisi Queensland Metal Finishing Company Pty Ltd PO Box
6198,UPPER MOUNT GRAVATT,QUEENSLAND
Australia, 4122 Ph:+61 7 3849 6460 Fax: +71 7 3849 7302 E-mail
mariopen@ozemail.com.au
*******************************

George Cushnie
NMFRC
http://www.nmfrc.org