Weight Loss of Plated Metals Heated in Vacuum

摘要

A series of experiments were conducted with 0.5 mil plated coatings on steel exposed to heat in vacuum. The plated coatings were cadmium, zinc, lead, nickel, and tin. Test conditions were exposure to vacuum at 0.000015 torr and temperatures from 200F to 675F. Periodic weight change measurements were made in room atmosphere using an analytical balance. Only slight variations of weight were observed with tests of lead, nickel and tin. Cadmium volatilized at rates of 3.0 to 7.6 mgm/sq cm day for temperatures at 400F. Zinc coatings behaved in an unusual manner. An initial rate of weight loss occurred at 435F only to decrease to zero at 450F with apparent constant weight. With increased temperature a rate of loss was resumed and rates of 4.5 to 6.5 mgm/sq cm/day occurred at 550F to a total loss of 90% coating weight. (Author)