A study on weathering steel bolts for transmission towers

This study aimed to develop weathering steel bolts (WSB) to solve galvanic corrosion problems between weathering steel and hot-dip galvanised bolts (HGB). A weathering steel wire rod for a cold-forming bolt was produced and then processed into grade 8.8 WSB. The microstructures, mechanical properties, and corrosion properties of the WSB were investigated by metallography, tensile, toughness, and cyclic immersion corrosion tests (simulated industrial atmospheric environment). A galvanic corrosion evaluation experiment was used to study the galvanic effect. The results revealed that the final microstructure of WSB was tempered sorbite. The tensile properties, wedge load, proof load, impact toughness, and hardness of WSB not only met the standard requirements of ISO 898.1 but also showed good comprehensive mechanical properties. The corrosion rates of the cylinder WSB, cylinder 20MnTiB steel bolt (MSB), and cylinder Q355 hot-rolled weathering angle steel (WAS) after 240 h cyclic immersion corrosion were 1A5, 2.34, and 1.81 g/m(2).h, respectively. The results showed that the corrosion resistance of WSB was superior to that of MSB and slightly better than that of WAS. The difference between the galvanic couple potentials of the coupled WSB-WAS was 14 mV, which means that the galvanic corrosion effect can be ignored. (C) 2020 Elsevier Ltd. All rights reserved.