A novel self-repairing hydrophobic composite coating for anti-corrosion protection of sintered Nd-Fe-B

In this paper, a corrosion-resistant glutamic acid (Glu)-Cu-Nano-Al2O3 composite coating with both hydrophobicity and self-healing characteristics was electrodeposited on the sintered Nd-Fe-B surface. The influence of the amount of Nano-Al2O3 added in the acidic Cu2+-glutamate (Glu2−) solution on the performance of the composite coating was studied, the results show that Nano-Al2O3 inclusion can make the surface of the composite coating appear papillary particles and make the composite coating hydrophobic. By analyzing the products of the composite coating after corrosion in 3.5% NaCl solution, it is shown that the codeposition copper dihydroglutamate (CuGlu2H2) and Glu particles in the composite coating are released and dissolved in the solution with pH = 6.5 after copper corrosion, and then complexed with Cu2+produced by corrosion to form an insoluble copper glutamate (CuGlu) passive film, which was deposited on the corroded coating to achieve self-repairing function and prevent further corrosion. The hydrophobicity and self-repairing function of the composite coating ensure that the sintered Nd-Fe-B has excellent corrosion resistance.