Design and Fabrication of a Sandwichlike Zn/Cu/Al–Zr Coating for Superior Anticorrosive Protection Performance of ZM5 Mg Alloy

Abstract

A new three-layered film was fabricated on magnesium (Mg) alloy via electroplating to guard against corrosion in a chloride aqueous environment, which consisted of an underlying double-layered zinc/copper (Zn/Cu) and a top aluminum–zirconium (Al–Zr) layer. The Zn/Cu underlayers not only impeded the galvanic corrosion between the Al–Zr coating and Mg alloy but also improved the adhesive ability between the substrate and the upper Al–Zr layer. Herein, we discussed the nucleus sizes of Al–Zr coatings at the stage of nucleation carried out with different contents of ZrCl4 in AlCl3–1-butyl-3-methylimidazolium chloride ionic liquid. The sandwichlike three-layered Zn/Cu/Al–Zr coatings were systematically investigated by surface morphology, phase structure, hardness, anticorrosion performances, and first-principles calculations. The corrosion current density declined from 1.461 × 10–3 A·cm–2 of bare Mg to 4.140 × 10–7 A·cm–2 of the Zn/Cu/Al–Zr3 sample. Neutral salt spray testing demonstrated that the Zn/Cu/Al–Zr3 sample showed no evident signs of corrosion after 6 days of exposure. The enhancement of the corrosion protection property was related to the fact that the application of the Cu layer changed the corrosion direction from initial longitudinal corrosion to extended lateral corrosion and the top Al–Zr coating hindered the transmission of aggressive ions. In addition, upon increasing the Zr content in the alloy films, the Fermi energy reduced initially and then increased. The Al–Zr3 alloy with 8.3 atom % Zr showed the lowest Fermi energy (−3.0823 eV), which exhibited the most efficient corrosion protection. These results showed that the prepared three-layered coating provided reliable corrosion protection to Mg alloy and may thus promote its practical applications.

Robust Self-Healing Graphene Oxide-Based Superhydrophobic Coatings for Efficient Corrosion Protection of Magnesium Alloys

“…L and R L denote inductance and passivation layer resistance, respectively. The appearance of these two phase elements at low frequencies means the beginning of a pitting process . Furthermore, the EECs of OPG-Cu 2+ and POPG-Cu 2+ coatings are explained in more detail using the model in Figure d 2 .…”

“…The appearance of these two phase elements at low frequencies means the beginning of a pitting process. 48 Furthermore, the EECs of OPG-Cu 2+ and POPG-Cu 2+ coatings are explained in more detail using the model in Figure 8d 2 . Q c corresponds to the constant-phase element (CPE) employed instead of capaci- tance.…”

Optimisation of Corrosion behaviour and hardness of Ni-B4C Composite coated AZ31 Mg alloy using RSM

“…The Ni coating on AZ31 Mg with an acidic electrolytic bath showed an efficient result in the saltwater immersion test with a protective precoated copper layer beneath [26].The dual coating on Mg alloy with an intermediate layer for improved adhesion protects well the substrate from corrosion [27,28]. The addition of Boron Carbide (B 4 C) nanoparticles in the composite coating deteriorates the tribological properties of the coating.…”