Pitting resistance of reduced graphene oxide-layered double hydroxide reinforced aluminum composite coating deposited by cold spraying

Abstract

Cold spraying aluminum-based coatings are widely used for corrosion protection of metals such as steel and magnesium alloy. However, poor pitting resistance and short protection life are the shackles of aluminum-based coating. In order to solve this problem, this paper innovatively utilized the synergistic effect of reduced graphene oxide (rGO) and layered double hydroxide (LDH) to modify the coating efficiently. Al-GLG coatings were prepared by cold spraying rGO and LDH-modified aluminum powders. The structure, composition and corrosion resistance of the Al-GLG coating were analyzed and compared with that of unmodified Al-based coating and graphene-modified Al-based (Al-G) coating. As a result, the Al-GLG coating presents a continuous network GLG surrounding the deformed aluminum powder, and this special coating exhibits pitting resistance and long life. The corrosion current density of the Al-GLG coating is only 0.01287 μA·cm−2, which is three orders of magnitude lower than that of the Al-based coating, and its pitting potential is about −0.24 VSCE, which is over 540 mV higher than that of the Al-based coating. During the full immersion text, the Al-GLG coating keeps the largest Rc (7.21×104 Ω·cm2) and low-frequency impedance modulus|Z|0.01Hz (3.66×104 Ω·cm2). The corrosion resistance mechanism of the Al-GLG coating was investigated via field emission scanning electron microscope (FE-SEM), X-ray diffraction (XRD), Raman and X-ray photoelectron spectroscopy (XPS), respectively. The excellent pitting corrosion resistance of the Al-GLG coating is attributed to the synergistic effect of the shielding effect of reduced graphene oxide and the ion exchange inhibition effect of LDH.