Initial comparison of pitting resistance of alloys for potential geothermal applications.

摘要

In order to use the energy available from geothermal sources, brines of a variety of compositions and temperatures have to be handled. Much of the hardware has consisted of metals, such as used in casings, pipes, valves, turbines, heat exchangers and others. When the pH is not very acid, and oxygen is absent, the brines are not very corrosive. However, there are instances where conditions cause accelerated corrosion. The present work was undertaken to examine one particular form of corrosion, pitting, which is encountered fairly often, and causes early failures in many industries because it is so localized. A number of alloys have been examined in the laboratory for their resistance to pitting corrosion in chloride media. The electrochemical procedure of determining pitting potentials was used. It was found that the most meaningful results could be obtained by increasing the aggressiveness of the test solutions as the resistance to localized attack of individual members of the series of alloys increased. The outcome of the experiments was the creation of a ranking of a large number of alloys according to their performance in the laboratory test program. The range of materials tested include carbon steel at the low end, with Hastelloy C-276 and Titanium at the top. 55 figs., 11 tabs.