Accelerated wet/dry corrosion test for buried corrugated mild steel

Abstract

In-service monitoring of the increasing network of buried corrugated metal pipes and culverts is essential to ensure continued operability via proactive assessments of potential failure and damage. A worst-case scenario for such structures is sudden failure resulting from deterioration due to prolonged corrosion effects. This paper proposes an accelerated laboratory corrosion test utilizing repeated wet/dry cycles to simulate the effects of chloride deposits on corrugated mild steel structures buried in cohesionless soil. The test was initiated by applying a 3.5% NaCl electrolyte solution to cohesionless soil above buried corrugated steel coupons, which were then subjected to repeated wet/dry cycles. To investigate the deterioration of mild carbon steel buried in a corrosive environment, the present work examines changes in the structural geometry and mechanical properties. The analysis shows how increasing the number of wet/dry cycles accelerates the corrosion and corresponding deterioration in steel strength, ductility, and hardness over a relatively short period of time. This paper also presents a mathematical model to provide an approximate prediction of corrosion damage for buried mild steel in soils, based on measurements of four physicochemical indicators at the interface between the steel surface and the surrounding soil. This could help to determine triggers for the maintenance or replacement of corroded buried mild steel structures, in the event of degradation in performance and workability.