Critical Chloride Corrosion Threshold of Galvanized Reinforcing Bars

Abstract

The chloride content required for corrosion initiation of galvanized reinforcing bars is determined. The bars conform to ASTM A767, except that no chromate treatment was applied to allow the degree of hydrogen evolution for untreated bars to be evaluated. Test results, along with results for conventional (ASTM A615), low carbon chromium (ASTM A1035, MMFX), and 316LN stainless steel reinforcement are compared with chloride surveys of bridge decks to obtain an average time to corrosion initiation. The average critical chloride corrosion threshold of galvanized reinforcement is greater than the threshold for conventional steel and lower than the threshold for ASTM A1035 and 316LN steel. Hydrogen gas evolution did not increase the porosity of the concrete in the non-chromate treated bars relative to that observed for conventional reinforcement. The average time to corrosion initiation at crack locations in bridge decks for galvanized steel is 4.8 years, compared with 2.3 years for conventional steel, and 15 years for ASTM A1035 steel. 316LN stainless steel will not corrode.