Studies on the development of activated binary clay and corrosion monitoring using embedded sensor

Abstract

Bentonite and marconite are the low resistance moisture retaining conductive backfill materials used in earthing applications. Both the products contains some drawbacks: bentonite has limited moisture retaining capacity and marconite has 15-20% impurities which will corrode the earth connections resulting in the loss of the system which are found to be very expensive. Taking into consideration of the above drawbacks, the present study aimed at developing a cost effective and highly conductive backfill material for earthing application with improved performance. For this study, commercially available bentonite and metakaolin (binary) clay was activated through physical, chemical and thermal treatments and the corrosion performance of binary clay was evaluated by using mild steel (MS) and galvanized (GI) steel Among the three activation methods, chemical activation method was found beneficial for mild steel in binary clay media. The conductivity of the chemically activated clay was 204.7 mS/cm, pH was 12.58, and the particle size distribution was found to be 40-50 mm indicates the better corrosion resistance and quite suitable for earthing applications. Chemical activation of the clay mainly involves the breaking of bonds and dissolution of the three-dimensional network structure of glass which in turn cause Na+ ions move closer to the center point of crystal structure and the solubility of SiO2 in clay markedly increases. Potential-time studies showed that galvanizing loses its coating property within ten days in all the three type of clays used. Activation process significantly reduced the corrosion rate (44 and 74 times) in the case of thermally activated (TAC) and chemically activated clay (CAC) respectively. Earth excavation studies were conducted to monitor the corrosion of MS and GI using embedded MnO2 sensor. This investigation opens up a lot of scope for utilizing activated binary clay for all earthing applications. (C) 2017 Production and hosting by Elsevier B.V. on behalf of King Saud University.