Comparative Susceptibility to Corrosion of Coated Expandable Bolts

Exposure of ground support systems to corrosive environments in underground hard rock mines can result in a significant degradation and loss of performance. This can have significant repercussions on the structural integrity of excavations in rock and potentially endanger the safety of mine workers. The use of corrosion inhibitor coatings can extend the useful working life of expandable rock bolts exposed to corrosive environments and act as a risk mitigating factor. This paper reports an investigation on the relative resistance to corrosion of six different variants of expandable bolts based on coating type and load capacity. The bolts were submerged for 226 days under two distinct water environments in an underground mine in the Sudbury basin. A systematic methodology was developed to assess the relative performance based on image analysis, SEM/EDX analysis of the exposed rock bolts, and changes in the morphological nature of the corrosion process. The results demonstrated significant variations in the performance of the various expandable coated bolts. This has significant implications in the material selection process for suitable rock bolts for specific corrosive environments.