Corrosion of a High Intensity Discharge Lamp

A connector subassembly for an automotive High Intensity Discharge (HID) lamp failed a 672 hour salt fog test. The connector backshell, made from either nickel plated or anodized A413.0 aluminum alloy, corroded heavily where a braided electromagnetic interference (EMI) shield was attached. Pitting corrosion enhanced by the presence of chloride ions and a galvanic cell is the cause. Five design concepts are evaluated and then ranked based on cost, assembly ease, schedule impact, and aesthetics. For the leading design, the nickel plated backshell remained, but a nickel plated braid and polymer clamp replaced the existing shield and clamp.