Summary for alkaline zinc barrel plating Discussion
Alkaline zinc barrel plating is discussed in terms of practical, empirical operating values rather than fixed theory. In the thread, Ted Mooney explains that a typical barrel-plating current density is about 0.5 amp/sq dm, which works out to roughly 195 amps and is not unusual for a 40 kg load. He notes that plating time depends on the thickness required: using the Metal Finishing Guidebook’s electrochemical equivalents, 0.001 inch (about 25 microns) at that current density would take about 160 minutes at 100% efficiency. He adds that commodity platers might only aim for 3.5 to 4 microns in a half hour, while 18 microns is a heavy deposit and would likely take at least 2 hours. His main caution is that barrel plating saves handling cost, but becomes less practical as thickness requirements increase.
Barrel plating is a method for plating parts in bulk rather than requiring the mounting of each item onto a plating rack.
Q. Plating load in 50 kg Barrel is 40 kg, and total area of the part is 390 dm.sq. To get minimum of 18 microns what is the current should be passed and time required to achieve this.
Kashi Sridhar
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July 17, 2025
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A. Hi Kashi,
Such numbers are always empirical rather than based solely on theory, but 0.5 amp/sq decimeter is probably a fairly typical current density ⇦ huh? for barrel plating, which would calculate out to about 195 Amps, and in my experience 200 A is not untypical for a 40 kg load.
The time required depends on the thickness you seek, but the “Electrochemical Equivalents” chart ⇦ huh? in the Metal Finishing Guidebook ⇨
says 14.3 A-hr/sq ft to deposit 0.001″ thickness, so if your current density is 0.5 A-dm2 or 5.38 A-ft2, you would deposit 0.001″ thickness or 25 microns in 14.3/5.38 hours, or 160 minutes at 100% efficiency ⇦ huh?.
if you were a commodity plater rather than a spec plater you’d probably get about 3-1/2 to 4 microns thickness in a half hour of plating, but 18 microns thickness is an awful lot (severe duty is 12-13 microns) — and will take probably take at least 2 hours. Barrel plating reduces handling cost compared to rack plating, but begins to get less practical when high plating thicknesses are required.
Please try to understand the background for these estimates so you can make appropriate adjustments to the figures.
Luck & Regards,
Ted Mooney, P.E. RET
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