Superhydrophobic coating for protecting bronze artefacts from electrolyte and gas corrosion

Corrosive solutions and gases are the most critical factors in the corrosion of metal artefacts. Preventing both electrolyte and gas corrosion without altering the appearance remains a challenge. In this paper, a superhydrophobic coating BTA-B72-FSiO 2 was prepared by stepwise treatments using benzotriazole (BTA), Paraloid B72 (B72) and fluorinated SiO 2 (FSiO 2 ) materials. The coating resulted in a colour difference of only 2.01 and no significant bleaching, in line with the requirements for artefact treatment. With a punctiform, rough structure, the surface exhibited superhydrophobic, anti-adhesive, anti-fouling and self-cleaning properties. The electrochemical corrosion current of the coated bronze was three orders of magnitude lower than that of the untreated substrate, and the impedance modulus at 0.1 Hz was four orders of magnitude higher than that of the untreated substrate. The coating showed no significant corrosion after one hour of immersion in HCl solution at pH = 1. The coating had excellent corrosion resistance due to the insulation of the corrosive electrolyte by air pockets on the FSiO 2 surface. Furthermore, the coated bronze substrate did not corrode significantly in the corrosive gas environment for 18 d. The inner B72 film provided a barrier to corrosive gases, making the coating resistant to gas corrosion. Finally, the synergistic effect of FSiO 2 and B72 provided dual protection against corrosive electrolytes and gases. This coating is expected to offer a new way of protecting metal artefacts in complex environments.