NEW ELECTROPLATED BLACK COATING -- BLACK CHROMIUM

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Abstract:

A description is given of the electroplating of black chromium coating for use on instrument components to eliminate glare and to prevent corrosion. Plating is conducted in a solution of chromic anhydride and sodium nitrate for a period of 20 minutes at a current density of 30-60 ampsq dm and a temperature of 15-40C. A lead-tin alloy 7 percent tin is used as the anode, and the chromium oxide content in the solution is regularly checked by the Hull cell test for replenishment. Coating thickness determined by metallographic method is 4.8 microns at a 20 min period and current density of 60 ampsq dm. The coating, containing a mixture of 75 percent chromium and 25 percent chromium oxide can be directly plated on aluminum and stainless steel components, and on iron components with undercoats of low tin-containing bronze. Results from humid heat tests and salt fog tests showed that the black chromium coating exhibits a better quality than the black nickel coating or bluing. Defects likely to occur in plating and their remedies are also given.

Author(s):
Hsu Hsiao-feng,
Author Organization(s):
FOREIGN TECHNOLOGY DIV WRIGHT-PATTERSON AFB OH
Supplementary Note:
Edited trans. of Shang Hai Chi Hsieh (Mainland China) n2 p12-13 1965.
Pagination:
0011

Security Markings

DOCUMENT & CONTEXTUAL SUMMARY

Distribution:
Approved For Public Release
Distribution Statement:
Approved For Public Release; Distribution Is Unlimited.

RECORD

Collection: TR
Identifying Numbers
Report Number(s):
FTD-HT-23-626-68
 Subject Terms
Communities of Interest:
Materials and Manufacturing Processes
Descriptor(s):
*CORROSION INHIBITION, *METAL COATINGS, *CHROMIUM, *ELECTROPLATING, CHINA, ELECTROCHEMISTRY
Field(s)/Group(s):
Coatings, Colorants and Finishes, Properties of Metals and Alloys
Keyword(s):
CHROMIUM OXIDES, TRANSLATIONS
Report Date:
1969 Mar 04