2012 Issue

47 Air Force landing gear is under a lot of stress, literally. High speeds plus heavy payloads mean extremely high stress; lives depend on them working every single time. T HERE IS SOME serious engineering in landing gear, and serious metal: vacuum forged, precisionmachined, high-strength steel. It does the job, day in and day out, in rain, snow, dust storms, and hostile territories. You would think it’s the toughest stuff around…until it meets oxygen or moisture, that is. All that wonderful heat-treated, mar- tensitic, high-strength steel is also highly susceptible to corrosion. Corrosion protection of high-strength land- ing gear parts is a multistage process, one that includes cadmium plating, chromate conversion coating, priming and painting. With over 60 years of fielded use, cadmium plating is well known, finely tuned, eco- nomical, and very effective. It is the benchmark for corrosion protection. There is only one problem with cadmium plating, the cadmium. Cadmium is toxic and carcinogenic. Plating and part-handling operators risk exposure from inhaled fumes, inhalation and ingestion of particulates, and absorption through skin. Furthermore, the plating solution includes a high concen- tration of cyanide ions, which are kept in solution by virtue of a pH greater than 11. An accidental mixing of acid with cadmium plating solution could release dangerous levels of hydrogen cyanide gas. Nor do the hazards end in the plating shop. There is also treatment and disposal of waste: rinse water from the process must undergo cyanide destruction and precipita- tion and removal of metals. Plus, the need for cadmium plating is never ending. As a sacrificial coating, cadmium corrodes pref- erentially to iron, so the cadmium plating Gears Go Green with Purple Coating at Hill AFB By Ruth Schaefer, and David Frederick GO GREEN | continued on page 48 Distribution Statement A, Approved for public release: distribution is unlimited, 11-12-06_EN_036(Final)