Evans, DW 2013, 'Emerging technologies in corrosion protection and acid resistance for ground support elements', in Y Potvin & B Brady (eds), Proceedings of the Seventh International Symposium on Ground Support in Mining and Underground Construction
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Corrosion in ground support elements remains an important area for industry focus, given the immediate concern for mine safety and operational efficiencies, as well as the hidden cost of longer term rehabilitation work. This paper discusses emerging technologies within the fields of corrosion protection and acid resistance that are providing new solutions for specific application areas within a number of ground support product designs.
Traditionally, anti-corrosion strategies have predominantly focussed upon Hot Dip Galvanising as a common industry solution. However, now complimenting this traditional solution, the more recent technology of Thermal Diffusion Galvanising is gaining interest within the Australian market, providing commercially viable solutions for a number of specific application areas that Hot Dip Galvanising cannot address.
Thermal Diffusion Galvanising is an alternate zinc based technology, which offers equivalent cathodic protection to that of Hot Dip Galvanising. Thermal Diffusion Galvanising has a comparatively deeper metallurgical bond to the steel substrate through various zinc-iron alloy layers, offering both increased adhesion and greater surface hardness. Beyond the capabilities of Hot Dip Galvanising, Thermal Diffusion Galvanising has specific applications of interest in high tensile steel grades, coating thickness consistency for threadforms, excellent torque/tension performance and greater flexibility with deformation. Thermal Diffusion Galvanising also continues to provide spark reduction properties on friction contact. Processing advantages also exist, with reduced concern for entrapped air pockets within the product design.
Research suggests that the greater percentage of iron alloy content within Thermal Diffusion Galvanising may offer a greater threshold for resistance to moderate pH environments. However, for low pH environments, zinc based coatings will rapidly degrade and do not provide any lasting protective benefit. Subsequently, neither Hot Dip Galvanising nor Thermal Diffusion Galvanising are suited to low pH conditions. Rather, barrier protection must be provided for ground support applications, either as a direct surface coating, or as a sheathing. Using the range of available technologies, product applications are under development that offer a suite of solutions – Thermal Diffusion Galvanising, acid resistant coatings and sheathing barriers.
This paper provides a technical summary of the detailed attributes of Thermal Diffusion Galvanising and its relative performance compared to that of Hot Dip Galvanising. The paper also details specific technologies for acid resistant barrier coatings. Applications of these technologies to ground support elements are then reviewed, relating this field of technology to specific product design areas and field applications.
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