Corrosion behaviors of hybrid ultrasonic phosphating coatings on carbon steel in simulated 150 °C hot-dry-rock fluids. (July 2020)

• Record Type: Journal Article
• Authors: Sun, Xiuxiu; Liu, Mingyan; Song, Junchao; Xu, Yangshuhan
• Is Part Of: Geothermics. Volume 86(2020)
• Publication Date: 2020-07
• Subjects: Carbon steel -- Ultrasonic phosphate coating -- Corrosion behavior -- Hot-dry-rock fluids -- Immersion test -- Corrosion electrochemical method; Hydrogeology -- Periodicals; Geothermal resources -- Periodicals; Énergie géothermique -- Périodiques; GEOTHERMAL ENGINEERING; GEOTHERMAL ENERGY; GEOTHERMAL EXPLORATION; Geothermal resources; Hydrogeology; Periodicals; Electronic journals; 621.44
• DOI: 10.1016/j.geothermics.2020.101807
• Languages: English
• ISSNs: 0375-6505

Abstract

Highlights: Ultrasonic phosphate coatings (UPCs) with and without SiO2 post-sealing were prepared. Ultrasonic improved the corrosion protection properties of phosphate coatings. The UPC was effective for corrosion protection even in 150 °C geothermal water. Coating resistance and charge transfer resistance increased 20 and 2 times respectively. Abstract: To improve the corrosion resistance of carbon steel in hot-dry-rock geothermal environment, Hybrid zinc phosphate coatings on carbon steel with and without sol-gel SiO2 post-sealing were prepared under ultrasonic conditions. The surface morphology, composition and crystal phases of the coatings were studied by SEM, EDS and XRD. The corrosion characteristics of the phosphate coatings in four types of simulated hot-dry-rock geothermal water were investigated by the immersion test and corrosion electrochemical method after immersion for 72∼336 h at 80∼150 °C. The results revealed that the ultrasonic phosphate (UP) coating suffered from homogeneous corrosion and the corrosion increased with increasing temperature. When the temperature increased from 80 °C to 110 °C, the influence of temperature on scaling was more significant than on corrosion. When the temperature further increased, corrosion became more severe. The UP coating and UP coating with SiO2 post-sealing (UP-SiO2 ) had the lowest corrosion current densities and the highest charge transfer resistance ( Rct ) due to better coverage, finer crystals and the seal of pores among crystal particles. The corrosion protection performance was improved because the ultrasonic phosphate coating prepared with SiO2 provided an effective barrier in simulated hot-dry-rock fluids.