In-situ Zn-Al layered double hydroxide conversion coatings prepared on galvanized steels by a two-step electrochemical method

• Published in: Corrosion science 2024-06, Vol.233, p.112057, Article 112057
• Main Authors: Xu, Teng, Yu, Lei, Hu, Ji-Ming
• Format: Article
• Language: English
• Subjects: Coating system; Corrosion protection; Layered double hydroxide; Pretreatment layer; Two-step electrochemical method
• ISSN: 0010-938X; 1879-0496
• DOI: 10.1016/j.corsci.2024.112057

Zn-Al layered double hydroxide (LDH) pretreatment layer was prepared by a novel two-step electrochemical method on galvanized steel surface from a precursor solution containing Al3+-only. In the first step, anodic currents are applied to Zn deposit to produce Zn2+ in solution near the substrate surface. Cathodic currents are then applied to ensure the cathodic deposition of LDH film. The obtained LDH coatings not only provide excellent adhesion to the metal surface, but also enhance the adhesion between metal substrate and the top epoxy coatings. The “LDH/epoxy” painting system can protect galvanized steel from rusting for at least 150 days. [Display omitted] •A novel two-step electrochemical method is proposed to prepare layered double hydroxide (LDH) pretreatment layer.•The electrochemical method takes only 5 minutes and can be performed at room temperature.•The obtained LDH pretreatment layer exhibits unique vertically-grown morphology.•LDH pretreatment layer greatly enhanced the adhesion between metal substrate and the top epoxy coatings.•The “LDH/epoxy” painting system can protect galvanized steel from rusting for at least 150 days.