Protective Iron Boride Coatings Against Corrosion in Geothermal Wells

Abstract

The challenges facing production equipment in geothermal processing, e.g. piping systems, in terms of corrosion, and the causes of failures and degradation of steels used for processing equipment components are analyzed. As one of the surface protection options, to minimize these problems and to enhance the equipment performance, iron boride coatings obtained through thermal diffusion process can be proposed. The principles of formation of the iron boride coatings on steels produced by Endurance Technologies Inc. (ETI) are reported. As opposed to many coating technologies, the ETI thermal diffusion process provides high integrity of finished products without spalling and delamination on the entire working surfaces of components. The results of testing in different corrosion environments will be presented. The boride-based coatings with dense micro-crystalline structure successfully withstand the actions of high temperature/ high pressure water steam with a presence of H2S, CO+CO2, chlorides, hydrocarbons in simulating conditions tested in the autoclave and in the pressurized Atlas cell, as well as in strong acidic environments. These coatings also demonstrated minimal scaling and corrosion when the materials were immersed into the modeling mixes contained chloride salts with SiO2 or SiO2+Fe2O3 at elevated temperatures and into the brine solution at boiling. Iron boride coatings also have high hardness and wear resistance in sliding sand flows. Complex-shape and long components (tubing up to 12-m length) with inner or inner and outer protected surfaces can be manufactured, which will promote significant extension of the steel service life in harsh geothermal-related corrosion or corrosion-abrasion environments.