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Friction rock stabilizers (FRS) are routinely used to provide rock reinforcement to excavations in hard rock. Since the expiration of the original patent taken out in 1977, FRS are now available from multiple suppliers. The expectation that all FRS are equivalent, however, is not necessarily accurate. There are inherent variations in the design configuration, material chemistry/properties, and consequently in performance. In this context, a full traceability from steel grade and heat treatment to final product is critical. This paper reports the results of a QA/QC investigation aiming to identify the material properties for three equivalent FRS from the same supplier. A series of mechanical and accelerated corrosion tests highlighted the differences in these rockbolts. This work provides a template for a more comprehensive quality assurance programme to ensure compliance of FRS. This is critical when rockbolts, due to global supply chain constraints, are outsourced from multiple sources worldwide. [ABSTRACT FROM AUTHOR]

The influence of welding flash on the corrosion resistance of friction stir spot welded (FSSW) AZ31B was examined by mass loss testing complimented with the scanning reference electrode and microcapillary polarization techniques. The microstructure of the flash was characterized by optical microscopy and the use of tungsten carbide tracer and correlated with the corrosion morphology of the joints. It was observed that the flash increased the corrosion rate of the welds, and its removal can reduce the corrosion rate by 20%. The increase in susceptibility for corrosion was explained by examining the electrochemical characteristics of the flash, and in particular to show the presence of a second stir zone (SZ) region in the flash. The electrochemical properties of the flash were correlated to second phase particle dissolution using a detailed microscopy analysis. The coupling of the two regions resulted in the formation of a local galvanic cell in the flash, leading to accelerated corrosion. Increases in dwell time and/or rotational speed of the tool during FSSW resulted in the formation of a larger SZ region in the flash, and produced a greater cathode to anode ratio. [ABSTRACT FROM AUTHOR]