Preparation and Protection Mechanism of Anticorrosive Lubricating Coatings

The coupling effect of wear and corrosion intensifies the damage and failure of key moving parts of high-end equipment, leading to a significant reduction in their service life. It is expected to solve the above problems by introducing the anticorrosive filler and solid lubricant into the polymer binder to prepare the protective coating. However, at present, most researches on organic bonded coatings with corrosion inhibition performance focus on the corrosion resistance of coatings, while the influence of corrosion inhibitors on the tribological properties of coatings is not clear, and organic bonded coatings with corrosion inhibition and excellent tribological properties are rarely reported. At present, among the corrosion inhibitors used for organic coatings, chromate is the most effective and widely used, among which strontium chromate (SrCrO₄) shows good compatibility, and its solubility is low and there is still enough dissolution to ensure its corrosion inhibition. Based on the corrosion inhibition characteristics of SrCrO₄ and the low surface energy and low shear characteristics of polytetrafluoroethylene (PTFE), the functional integrated strontium chromate/ polytetrafluoroethylene/phenolic epoxy (SrCrO₄/PTFE/EPN) coatings with excellent corrosion resistance and tribological properties were prepared. The effects of SrCrO₄, PTFE and corrosion friction medium on tribological properties and electrochemical corrosion resistance of coatings were investigated by CSM friction and wear testing machine and P4000A electrochemical workstation. In order to focus on the corrosion inhibition and protection mechanism of SrCrO₄ in phenolic epoxy coating, we firstly introduced SrCrO₄ into EPN coating, and studied the surface morphology and electrochemical corrosion resistance of the coating. It was found that, especially when the introduction amount of SrCrO₄ was 4% of the resin mass, the surface of the coating was flat and compact with no obvious pores. SrCrO₄ introduced can be uniformly embedded into the coating, and fill the intrinsic defects of the coating, which can improve the barrier performance of the coating, and can chemically react with the substrate to produce a uniform and stable passivation film at the interface. Similarly, the passivation effect was the best when the added amount was 4% of the resin mass. It presented A high low-frequency impedance modulus (1.06×10¹¹ Ω∙cm ²) and the lowest corrosion current density (0.28×10⁻¹⁰ A/cm²), which effectively improved the corrosion resistance of the coating and had little influence on the tribological properties of the coating. The surface energy of SrCrO₄/EPN coating was decreased by adding PTFE, and the water contact angle of the coating increased by 31% from 73.4° to 96.0°, which made the coating change from hydrophilic to hydrophobic, and further increased the barrier property of the coating. The corrosion resistance and tribological properties of SrCrO₄/PTFE/EPN coating were further investigated. The results showed that SrCrO₄ can still react on the substrate interface through corrosion inhibition, resulting in a corrosion inhibition passivation layer, which can effectively improve the corrosion resistance of the coating. The introduction of PTFE not only further improved the shielding properties of the coating, but also significantly reduced the friction coefficient and wear rate of the coating. The friction coefficient was as low as 0.059, which was reduced by 73.90% compared with the pure EPN coating, and the wear resistance was increased by 3.2 times. Under the corrosive medium condition of 3.5% NaCl solution, SrCrO₄/PTFE/EPN coating exhibits lower friction coefficient, and SrCrO₄ in the coating can provide passivation protection for the friction pair. Passivation film in the form of Fe and Cr oxide hydroxide or crystallization hydrate is formed on the friction dual surface through passivation reaction. Thus, the wear intensification caused by the corrosion of friction pair is inhibited.