Fluorine-free superhydrophobic CuO-modified coating for enhanced corrosion protection of steel in oilfield-produced water

Purpose Corrosion remains a persistent challenge for in-service steel, while conventional anti-corrosion methods are often costly or require harsh pretreatment; thus, a facile chemical displacement deposition combined with octadecyltrimethoxysilane (ODTMS) modification was developed to fabricate a fluorine-free superhydrophobic coating on pipeline steel. The micro/nanoscale rough structure inhibits corrosive media invasion and improves corrosion resistance in harsh oilfield environments. Design/methodology/approach The microstructure and chemical composition of the coatings were characterized by scanning electron microscope, 3D confocal microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. Wettability and optimal preparation parameters were evaluated through water contact angle, sliding angle and electrochemical measurements. Immersion tests were conducted in NaCl solution and oilfield-produced water, and a corrosion kinetic model was established to elucidate the underlying protection mechanism. Findings The optimized coating was prepared by 50 s copper deposition followed by 60 min ODTMS modification, achieving a maximum water contact angle of 164° and a sliding angle of 4.8°, together with excellent electrochemical corrosion resistance. Its superior anti-corrosion performance originates from the micro/nanoscale rough structure that endows favorable surface wettability. Immersion tests reveal that oilfield-produced water induces more severe corrosion than NaCl solution. Originality/value This eco-friendly, fluorine-free superhydrophobic coating can be easily fabricated for pipeline steel. On Q235B steel, it achieves a corrosion inhibition efficiency of 92.6% and exhibits excellent stability. The coating forms an isolating barrier that greatly suppresses the corrosion of the steel substrate. A corrosion kinetic model is established to elucidate its protection mechanism, providing theoretical guidance for the design of anti-corrosion coatings under harsh oilfield service environments.