Abstract
Corrosion tests were made on various stainless steels to make geothermal power plants of binary cycle systems available for dilute acidic geothermal brines. Corrosion tests were made in a hydrochloric acid type brine at Onikobe in Miyagi prefecture and in a sulfuric acid type brine at Kurokawa in Kumamoto prefecture. Using test results and assuming the service period for 15 years, rough values of pit depth and reduction of plate thickness by uniform corrosion of evaporator tubes which were especially under severe corrosion conditions were presumed.
A brief summary of main results is as follows.
(1) Approximate values of maximum pit depth of evaporator tubes including weld joints after 15 years usage were presumed to be 0.6 mm for SUS 316 and 1.0 mm for 19Cr-2Mo steel.
(2) Approximate values of maximum pit depth of SUS 410 and SUS 304 were presumed to be larger than those of SUS 316 and 19Cr-2Mo steel. Particularly deep pits were presumed to be found on SUS 304 immersed in the brine at Kurokawa for 15 years, according to oxygen dissolved in the brine.
(3) Reduction of plate thickness by uniform corrosion is quite smaller than pit depth. Especially the former of SUS 316 and 19Cr-2Mo steel after the 15 years service period was presumed to be negligible compared with the latter.
