Investigation of Protective Performance of a Mg-Rich Primer Containing Aluminum Tri-Polyphosphate on AZ91D Magnesium Alloy in Simulated Acid Rain

Abstract

Mg-rich primer (MRP) containing aluminum tri-polyphosphate functions via a galvanic mechanism to protect AZ91D alloy from corrosion in the 3 wt % NaCl solution. However, its protective performance can be strongly affected by the testing environment. Therefore, it is important to investigate the performance of the primer on magnesium alloys in an acid rain environment. In the present study, the protective performance of MRP with or without aluminum tri-polyphosphate was investigated via open circuit potential (OCP), electrochemical impedance spectroscopy (EIS), scanning electronic microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) in the simulated acid rain. Compared to the primer without aluminum tri-polyphosphate, the MRP containing aluminum tri-polyphosphate pigments exhibited better protective performance in the simulated acid rain condition. In the initial stage, the acidic condition prompted the aluminum tri-polyphosphate pigments to release phosphates and H+ to form magnesium phosphates on Mg particles, retarding their consumption rate. The Mg-rich primer with aluminum tri-polyphosphate can provide cathodic protection to AZ91D alloy for about 49 days in the simulated acid rain solution. Simultaneously, the corrosion products of Mg particles, magnesium oxides and phosphates, precipitated on the Mg particles and improved the stability of the primer. In addition, a protective film, consisting of magnesium oxides and phosphates, formed on the AZ91D substrate. Consequently, all these factors contributed to the long cathodic protection and improved corrosion resistance of MRP containing aluminum tri-polyphosphate in the simulated acid rain.

High-Performance Full Sodium Cells Based on MgO-Treated P2-Type Na0.67(Mn0.5Fe0.5)1−xCoxO2 Cathodes

“…In the Mg 1s range, the peak can be deconvoluted at two components centered at 1303 and 1304 eV. These values are attributed to Mg atoms in the structure of layered oxides and in a separate MgO phase, respectively [54]. The observation of the complex peak of Mg1s supports, once again, the XRD and vibrational data on the partial incorporation of Mg 2+ ions in layered oxides.…”

The Waterborne Superamphiphobic Coatings with Antifouling, High Temperature Resistance, and Corrosion Resistance

“…Furthermore, the polytetrafluoroethylene-modified aluminum tripolyphosphate-modified silica (PTFE-ATP-SiO 2 ) composite coating possessed good adhesion (grade 1), thermal stability (<425 °C), excellent antifouling, and impact resistance. More importantly, the modified ATP improved the density of the PTFE-ATP-SiO 2 composite coating and was regarded as an anticorrosive material to enhance corrosion resistance. , After 20 days of immersion in 3.5% NaCl solution, the PTFE-ATP-SiO 2 composite coating still had 89.1% protection efficiency. This work is expected to provide a facile idea and method for the preparation of waterborne superamphiphobic coatings with high temperature resistance and anticorrosion by one-step spraying.…”

“…More importantly, the modified ATP improved the density of the PTFE-ATP-SiO 2 composite coating and was regarded as an anticorrosive material to enhance corrosion resistance. 40,41 After 20 days of immersion in 3.5% NaCl solution, the PTFE-ATP-SiO 2 composite coating still had 89.1% protection efficiency. This work is expected to provide a facile idea and method for the preparation of waterborne superamphiphobic coatings with high temperature resistance and anticorrosion by one-step spraying.…”

Atmospheric Pressure Plasma Treatment of Magnesium Alloy for Enhanced Coating Adhesion and Corrosion Resistance

“…Selecting the proper protective coating to apply on a bare Mg alloy is challenging because a traditional polymeric coating (e.g., pure epoxy) does not provide good adhesion to Mg alloys, and corrosion may be accelerated if the coating is physically damaged [19]. For these reasons, metal particle composite coating matrixes (e.g., Al-/Mg-rich primer) have been investigated to provide the cathodic protection and improve barrier effects [19,20]. The particles selected for the composite matrixes were limited to a few active metals, such as pure Mg and Al, because of the internal galvanic corrosion caused by the second phase or impurities.…”

“…The coatings also benefit from fast process time, low cost, and good application on various metal surfaces. Various coatings, such as electrochemical conversion [8,9], anodizing [10,11], electroplating [12], cold spray [13,14], superhydrophobic coating [15][16][17][18], and organic primers [19,20], have been investigated for the protection of Mg alloy surfaces. The performance of a protective coating is greatly influenced by its adhesion to the substrate material.…”