Physical properties of electrodeposited chromium

Abstract

The following pro perties of chromium, deposited under a wide variety of plating conditions, 11ave bee n measured ; densi ty, hardn ess, tensile s trength, Young's mod ulus of elasticity, ductili ty, electr ical res istivi ty, and stress in t he deposit. The oxygen and h ydrogen content were d etermined. The effect o f heat treatments up to 1,200° C on certain of these properties has been determin ed, and so me work has been done on t he properties of chromium-iron alloys deposited from modifi ed chromi c acid solution s. A relation between the hydrogen alld oxyge n content of the deposits has been shown to exi st, and the effect of the oxygen co ntent on the physical properties has bee n studi ed.

Effect of chromium plating on the endurance limit of steels used in aircraft

“…In the present investigation, the densities of tubes of chromium were determined for each of the following conditions: "as deposited, " after heating at 193 0 0 (in boiling ethylene glycol) and after a second heating in h elium at 440 0 O. The densities wer e 6.95 gjcm 3 as plated, 7.01 gjcm 3 after h eating at 193 0 0 , and 7.09 gjcm 3 after heating at 440 0 O. Brenner [9] indicated that changes in the volume of chromium on heating were isotropic. H ence, heating at 200 0 0 would tend to reduce the volume of the plated chromium.…”

“…Zapffe [8] has explained brittlen ess observed in bend tests on wire plated with chromium as due to hydrogen. Brenner, Burkhead, and J ennings [9] showed that approximately 95 percent of the hydrogen is removed by h eating chromium at 450° C. These facts suggest that the improvement in endurance limi t of specimens heated at 440° C is due to the expulsion of hydrogen. However, specimens heated at 200° C had in some cases only 50 percent of the endurance limit of unheated specimens, whereas data given by Brenner and coworkers showed that approximately half of the hydrogen was removed from the chromium by heating at 200° C. It is difficult, therefore, to see how the results of the fatigue tests r eported here can be attributed directly to hydrogen embrittlement.…”

“…2 in electrolytically deposited chromium. Brenner, Burkhead, and J ennings [9] reported that the r esidual tensile stresses in chromium plated to a thickness of 8 X 10-4 in. increased from approximately 15,000 lbjin.…”

“…The formation of cracks in chromium plating is usually attributed to the rupture of the deposit as the result of high r esidual tensile stresses [9] . The presence of cracks in the chromium, therefore, 110 indicated at least partial relief of residual stresses.…”

Electrodeposition of high-purity chromium.

“…In a comprehensive study of the influence of plating variables on the diverse properties of chromium d€posited from sulphate-catalysed baths , Brenner et al ( 8 ) determined the oxyg~n and hydrogen contents of the various deposits.…”