Influence of high temperature and high acidic conditions on geopolymeric composite material for steel pickling tanks

Traditionally, most equipment that was used for containing corrosive solutions and fumes for the steel industry was fabricated from steel with a rubber-lined interior. An additional acid-resistant brick lining was used to protect the rubber lining and also to act as thermal insulation. This investigation focussed on a geopolymer material that would simultaneously solve the two issues, recurrent acid leakage from the brick-lined structure and minimal thermal stress during operation. The scope of this project was limited to identify the extent of weight loss in a strong HCl acidic environment for a standard geopolymeric composite at 90 °C. Accelerated tests on geopolymer samples were conducted over 110 days and the weight loss results were extrapolated over a time period of 300 days. Visual inspection showed that OPC had a reduced diameter after 40 days of acid exposure, and therefore, the overall acid penetration for OPC was significantly higher than GPC. The mechanism of weight loss or material degradation was not the key aim in this investigation, rather we aimed to obtain a new composition to withstand highly acidic condition (which are not encountered with ordinary Portland cement (OPC) concrete, e.g. in sewage conditions). The average weight loss of a theoretical slab of geopolymer sample in accelerated test conditions (90 °C and 22% HCl) is found to be 1.8 wt% in 60 days for single-face exposure and the average thickness loss predicted for a 40 mm thick slab is about 3.5% after 300 days of exposure in operating conditions of 18% HCl and 80 °C after reaching steady-state weight loss. This is significantly better compared to a standard concrete and brick slab or steel-lined rubber slab. This initial investigation indicated that with further scientific investigation and understanding of the material, the application could be broadened to further minimise acid corrosion over longer time periods (10 years).