Letter 19172 Alkaline vs acid zinc +++ Which is better....alkaline or acid zinc? Alot of the responses are 3-5 years old and I am wondering if tecnology has changed. The parts average 8 square feet requiring throw into low current density areas. Brightness is important but not crucial. John Skuchas - Upland, CA, USA First of two simultaneous responses -- +++ Yes, alkaline zinc offers better throw. As a very broad and general rule of thumb, yes, alkaline zinc has improved to the point where it is usually the first choice for rack plated parts. Ted Mooney, P.E.  finishing.com Brick, New Jersey Second of two simultaneous responses -- +++ Alkaline non-cyanide zinc plating is generally better than acid zincs where a good throw into low current density areas is required. Modern formulations can give a brightness which although not equal to, is fast approaching that of acid zinc. Distribution from alkaline non-cyanide solutions is also far superior to that which could be expected from acid zincs. Dougie Lightfoot - Fife, Scotland +++ Alkaline will throw better, Acid is slightly brighter. Once I had a client who needed both, so we alkaline plated first to throw into the deepest recesses, then we topped off with a bright acid zinc. We used a HCl dip in between. Since the acid zinc "saw" only pure zinc, it did not build up in iron like a conventional application would have done. Your zinc vender would love this advice, but just try the alkaline by itself first. Robert H Probert Robert H Probert Technical Services Garner, North Carolina Editor's note:        Mr. Probert is the    author of Aluminum How-To / Aluminio El Como Dear Reader, please -- Answer or follow-up on this subject (in non-commercial fashion).   Post a new question or inquiry on a different subject.

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