Letter 24065

Standard salt spray hours for zinc plating

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Is there a standard on how many salt spray hours before red rust. I am looking particularly for Zinc Plate .0004-.0006" Plus Yellow Chromate per ASTM B-633 [link is to spec at TechStreet] TY2, SC3, Plus MacDermid JS 500 Ultraseal. Zinc Plate 5 Micrometers Min, Yellow Chromate per ASTM B633, TY II, SC. 1. And, Zinc Plate 5 Micrometers Min, Bright Chromate per ASTM B633, TY III, SC. 1

Pat Donlon
plating shop - Rochester, New York

Hi, Pat. I don't know of a universal standard for this, but we have many threads on line that will provide some info. For example, letter 46231 implies that 120 hours to white rust and 240 hours to red rust is easily achievable with 8 microns (about .00032").

Several threads here suggest that if you are aiming for much more than that, switching to a zinc alloy plating may be a more productive route than thickening the plating, and tweaking the chromate and final seal. Good luck.

Regards,

Ted Mooney, P.E.  finishing.com Brick, New Jersey