Ceramic-filled epoxy, ethylene methacrylic acid (EMAA) and ethylene tetrafluoroethylene (ETFE) coatings were evaluated for corrosion protection in a biochemical process to treat geothermal residues. The epoxy was brush applied whereas the other coatings were thermal sprayed. Atlas cell and peel strength tests were performed in aggressive environments including hypersaline brine and sulphur oxidizing bacteria (Thiobacillus ferrooxidans). It was found that the polymers were resistant to chemical attack and biodeterioration at the test temperature of 55°C. Corrosion of mild steel substrates coated with EMAA and ETFE occurred in Atlas cell tests that simulated an uninsulated lined reactor and this resulted in decreased adhesive strength. The ceramic-filled epoxy provided better substrate protection than the EMAA and EWE. Insulation of the reactors may improve coating performance since tlus would decrease the thermal gradient which affects permeation. The results of the research are also applicable to low temperature geothermal applications.
Geothermal Resources Council Transactions,
Vol. 22, no. (Sep 1998), pp. 425-429