Corrosion of Steel Girder Bridge Anchor Bolts

Corrosion of anchor bolts has been revealed by inspections of steel girder bridges throughout the State of Georgia. Of Georgia’s steel girder bridges, 411 (27%) were found to be experiencing anchor bolt corrosion, with a median age of 39 years when corrosion was first reported. From field investigations of bridges built prior to 1990, A36 carbon steel anchor bolt corrosion is attributed to the formation of corrosion macrocells with the bolt’s concrete embedment and the buildup of dirt and debris at the bearing site. In bridges built post-1990, Type 304 stainless steel anchor bolts may be susceptible to galvanic coupling and localized forms of corrosion. By laboratory based experimentation, it was concluded that A36 carbon steel bearing components may experience active corrosion, with accelerated corrosion rates due to macrocell and galvanic coupling effects in an exposed pH 7.5 environment. It is noted that galvanic coupling may occur on Type 304 stainless steel anchor bolts, but further research is necessary. Type 304, 316, 2101, and 2205 stainless steels were tested for localized corrosion. Only Type 304 stainless steel exhibited localized corrosion when polarized to potentials much higher than anticipated in the Georgia bearing environment. Therefore, it may be concluded that each of the candidate alloys tested is acceptable for use as anchor bolts in Georgia. However, special consideration should be given to the use of Type 304 stainless steel in more aggressive environments, such as industrial settings or regions where deicing salts/chemicals are used frequently.