Surface condition effects on critical chloride threshold of steel reinforcement

TLDR: In this article, the critical chloride threshold values of five uncoated steel reinforcement types (ASTM A 706, ASTM A 615, microcomposite, stainless steel 304, and stainless steel [SS] 316LN) with as-received and polished surface conditions were quantitatively determined using the accelerated chloride threshold test procedure.

Abstract: Deicing and anti-icing salts and seawater are the main sources of chloride ions that cause the corrosion of steel reinforcement embedded in reinforced concrete (RC) bridge and marine structures. This article reports on a study undertaken to evaluate the influence of the steel reinforcement surface condition on the corrosion performance. In the study, the critical chloride threshold values of five uncoated steel reinforcement types (ASTM A 706, ASTM A 615, microcomposite, stainless steel 304, and stainless steel [SS] 316LN) with as-received and polished surface conditions were quantitatively determined using the accelerated chloride threshold (ACT) test procedure. Micrographs of the surfaces (characterizing the mill scale and surface topography) for all steel reinforcement types were obtained using both optical and scanning electron microscopy (SEM). Results showed that the mean critical chloride threshold values increased with the complete removal of the as-received surface and with surface polishing for the ASTM A 706, microcomposite, and stainless steel 304 reinforcements. In addition the mean critical chloride threshold values decreased with the complete removal of the as-received surface and with surface polishing of the ASTM A 615 and SS316LN steels. The authors conclude that removal of the mill scale on the microcomposite steel reinforcement showed a significant improvement in the critical chloride threshold and removal of this mill scale may be economically justified.