Hot Dip Versus Electroplating Versus Phosphating
Q. I HAVE A QUERY ON HOT DIP GALVANISING VERSUS ELECTROPLATED VALVES.
WHICH OF THE PROCESSES IS BETTER. WHAT IS THE COATING THICKNESS ACHIEVED IN HOT DIP AS WELL AS ELECTROPLATED VALVES.
ALSO CAN CAST STEEL AND CAST IRON VALVES BE GALVANISED BY BOTH PROCESSES.
PLEASE TELL ME IF PHOSPHATING IS A BETTER SOLUTION FOR GALVANISING
KVAERNER POWERGAS INDIA LTD - pune, maharashtra, india
A. Hot dip galvanizing and electroplating both deposit essentially pure zinc metal as a sacrificial coating. There is an old truism: "Zinc is Zinc". So it doesn't matter which way the zinc was put on, only the thickness matters. Practically, though, zinc plating is more economical for thin coatings up to say .0006" and galvanizing is more economical for heavier coatings.
Cast steel and cast iron can be electroplated; I'm not sure of practical limitations on galvanizing of these metals.
Phosphatizing offers almost no corrosion resistance itself, but it vastly improves the corrosion resistance of painted finishes.
Ted Mooney, P.E.
Pine Beach, New Jersey
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