Posted by Willy-N on Tuesday, June 24, 2003 at 7:01PM :
In Reply to: Re: No paint on originals posted by Tom J. on Tuesday, June 24, 2003 at 6:03PM :
Hydrogen Embrittlement - High carbon and high strength steels having
a hardness greater than 35 Rockwell C are susceptible to embrittlement
caused by absorption of hydrogen in the processing of the steel in pickling,
cathodic cleaning or plating operations. Zinc and cadmium plating
can cause this embrittlement on high strength steels used to make
springs, lock washers, fasteners and the like. The phenomenon of delayed
cracking by hydrogen embrittlement has been studied by hundreds
of workers but is still not thoroughly understood. There is no general agreement on the processing cycle for cleaning and plating such steels
with zinc or cadmium which will reliably avoid the embrittlement. There
is agreement that susceptible steel parts should be heated after plating
to reduce danger of subsequent cracking. Baking at 191°C (375 °F) for four
hours is a widely used precaution recommended in ASTM Designation B
242. High-efficiency chloride plating processes which generate very small
amounts of hydrogen during operation are available for zinc and cadmium
requirements. The use of these processes enables a bright, ductile deposit
of zinc or cadmium to be plated directly on cast iron, malleable iron
or steel with greatly reduced possibility of inducing hydrogen
embrittlement. Mechanical plating can also be used to eliminate this
problem since the process imparts no significant absorption of hydrogen.
Got this off the net. Lot of information on it. Mark H.
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