Structure and performance insights in La modified carbon quantum dots-epoxy coating with efficiency corrosion and wear resistance

Epoxy resin is a very versatile material but has limited corrosion and wear resistance. Carbon quantum dots are a new type of corrosion inhibitor material with good dispersibility. In this paper, lanthanum nitrate, ethylenediamine and citric acid were mixed to prepare lanthanum‑nitrogen doped carbon quantum dots (La/N-CQDs) by a hydrothermal method, which could show good dispersion and compatibility in epoxy resin. Meanwhile, a series of La/N-CQDs modified La/N-CQDs@EP coatings with long-term corrosion resistance and friction reduction were successfully prepared on the NdFeB surface by spin-coating method. The results of electrochemical tests and tribological tests show that the La/N-CQDs doped EP composite coatings could effectively enhance the anti-corrosion and anti-wear protection to the NdFeB surface. The La/N-CQDs@EP composite coating doped with 2 wt% La/N-CQDs showed the lowest corrosion current density and remained the highest impedance modulus after 14 days of immersion in 3.5 wt% NaCl solution. While the La/N-CQDs@EP composite coating doped with 1.5 wt% La/N-CQDs possess relatively low friction coefficient and wear rate. The excellent corrosion protection and wear resistance of the La/N-CQDs@EP coatings were mainly due to the enhanced interfacial bonding, and improved the densification of the epoxy resin structure. These indicated that La/N-CQDs modified EP composite coatings could effectively control the corrosion and wear loss of NdFeB in some harsh environments.