Galvanic Behavior Database for Titanium-Steel Alloy Couples

Report No. ARL-TR-2812
Authors: Ralph P. I. Adler, Christopher E. Miller, and Brian E. Placzankis
Date/Pages: September 2002; 29 pages
Abstract: Future lightweight armor for the next generation of lighter material will probably use titanium alloy components. These will form galvanic couples with other materials and may induce phenomena accelerating the corrosion rate of those metals less noble than titanium. The project objective was to evaluate the magnitude of galvanic corrosion between typical ferrous and titanium alloys. Electrochemical and accelerated corrosion measurements on both bare and Chemical agent resistant coatings (CARC)-coated Ti/steel samples determined accelerated corrosion rates. Samples with and without "X-scribed" defects in the CARC coating were evaluated. Electrochemical studies on bare Ti/steel couples validated accelerated steel corrosion rates but found that intact CARC coatings mitigate corrosion. Even for X-scribed samples, the rapid corrosion product buildup in the defect reduced galvanic currents by two orders of magnitude. Studies with "Joint A Assembly" CARC-coated samples (phase I: bolted sets of Ti/steel plates with intact CARC seals) had virtually no interface corrosion. After examination, the rebolted samples with compromised CARC seals had a second accelerated corrosion cycle (phase II); the moisture intrusion caused a severe buildup of interface corrosion. Thus Ti/Fe interfaces with defect-free CARC coatings can prevent buildup of iron corrosion products.
Distribution: Approved for public release
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Last Update / Reviewed: September 1, 2002