Advanced iron boride coatings to enhance corrosion resistance of steels in geothermal power generation

Abstract

Iron boride coatings obtained by the CVD-based thermal diffusion process are proposed and evaluated for the first time for high-temperature corrosion and scaling conditions in geothermal power generation. The testing results in different corrosion environments are presented. The influence of structure and surface composition on the materials' performance is demonstrated. The dual-layer boride-based coatings successfully withstand the actions of high temperature/high pressure water and steam with a presence of H 2 S, CO + CO 2 , chlorides and hydrocarbons in simulating conditions and strong acidic environments. They demonstrated minimal scaling and corrosion when the materials were immersed into the modelling mixes of chloride salt solutions with SiO 2 or SiO 2 +Fe 2 O 3 at elevated temperatures and into the brine solution at boiling. These advanced ceramic coatings and technology should promote significant extension of the steels' service life in harsh geothermal-related corrosion environments.

Corrosion resistance evaluation of boron-carbon coating on ASTM A-36 steel

“…Consequently, Fe +2 ions are formed, and then react with OH − ions producing rust [24]. Although, Fe 2 B phase is a ceramic material with a high hardness [25] and high corrosion resistance [26]. It protects any surface against the attack of aggressive ions as Cl − ions, which are responsible for the steel corrosion.…”

Effect of B on Microstructure and Properties of Surfacing Layer of Austenitic Stainless Steel Flux Cored Wire

“…The surface of the base carbon steel is polished, the oxide scale is removed, cleaned with absolute ethanol, and then overlaid on the low carbon steel plate by means of MIG welding. Welding current 200 A, welding voltage 24 V, welding speed 10 cm/min, gas flow 12 L/min [ 5 ]. …”

“…The surfacing alloy has good corrosion resistance. Medvedovski [ 5 ] et al studied the high temperature corrosion of iron boride coating in geothermal power generation under different corrosion environments. The double layer boride-based coating has successfully withstood the effects of high temperature/high pressure water and steam, H 2 S, CO + CO 2 , chloride, and hydrocarbon in simulated conditions and strong acidic environment.…”

Research and Development on Coatings and Paints for Geothermal Environments: A Review

“…More recently, a study by Medvedoski et al, [158,159] investigated iron boride coatings deposited by pack CVD technology, for corrosion mitigation of carbon steel in downhole tubing equipment. In the work, coated specimens of 155-220 μm thickness and control carbon and stainless steel coupons, were exposed to six different environments: a) 1.5% NaCl, 1.5% CaCl, 0.3% H 2 S, 12.6% hydrocarbons, 17.7% CO, 69.4% CO 2 at 280 °C, 28 MPa, for 168 h, b) 15% HCl at 100 °C for 168 h, c) 70% H 2 SO 4 at 100 °C for 168 h, d) mixture of alkali and earth-alkali chloride salts at 370-416 °C for 672 h, e) partial immersion into salt mixes solution (to obtain steam), heated to 370 °C for 168 h, and f) salt mixes solution under boiling conditions at 110 °C for 4 to 7 h. Specimens after exposure were analyzed by visual examination, weight loss, and microstructural examination.…”