To combat expensive bridge deterioration caused by corrosion, this project investigated the feasibility of using dissimilar metal welds (DMWs) to protect highly corrosive locations while minimizing initial fabrication costs. The research evaluated welding corrosion-resistant steels—specifically ASTM A709 Grade 50CR and a potential alternative, ATI 412—to standard structural bridge steels (ASTM A36 and ASTM A709 Grade 50W). Initial weldability evaluations indicated that these DMWs are highly susceptible to solidification and cold cracking. However, researchers determined that utilizing lower heat input and a single-V with backgouge weld joint successfully eliminated these defects, allowing the crack-free DMWs to ultimately meet the mechanical property requirements of the AASHTO/AWS D1.5 Bridge Welding Code.

Despite satisfying basic mechanical standards, the DMWs exhibited severe vulnerabilities during corrosion and non-destructive evaluation (NDE) testing. The material combinations suffered from accelerated galvanic, pitting, and intergranular corrosion, particularly within the heat-affected zones of the weld interfaces. Furthermore, standard NDE inspection methods proved highly unreliable; radiographic testing produced artifacts that could mask flaws, while ultrasonic and phased array testing suffered from anisotropic behavior and wave refraction that caused defects to be mislocated or missed entirely. Consequently, because of these persistent corrosion and inspection challenges—compounded by long lead times and recent quality issues with 50CR steel—the Virginia Transportation Research Council recommends that VDOT avoid utilizing 50CR/412 steel in DMWs and continue to exercise caution when specifying 50CR steel to manage project risk.

Infrastructure Assets: Bridge, Highway Assets, Other Highway Assets
Resource Types: Research Report
Capabilities: Tools & Technology
Management Processes: Monitoring & Adjustment, Performance Reporting & Communication, Strategic Direction