Effect of heat treatment conditions on the passivation behavior of WE43C Mg–Y–Nd alloy in chloride containing alkaline environments

Abstract

Mg-Y-Nd alloy (WE43C or Elektron 43) is a heat treatable magnesium wrought alloy that can be used up to 250°C for aerospace application. This alloy has excellent mechanical properties (UTS: up to 345 MPa at room temperature) and improved corrosion resistance. Electrochemical passivation studies were conducted on this alloy under different heat treatment conditions in 0.1 M NaOH solution with the addition of chloride from 0 to 1000 ppm. The passive potential range typically extended to more than 1.5 VAg/AgCl. The transpassive potential was not dependent on the heat treatment condition of the alloy when the chloride concentration increased up to 500 ppm. However, pitting protection potential varied with the heat treatment condition when the chloride addition was 500 ppm or more. The specimen surface was analyzed using scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy to understand the passivation behavior of this alloy. The passivated surface of the WE43C specimens indicated that the surface layer consisted of MgO, Mg(OH)2, and rare earth oxide phases, and the heat treatment conditions did not significantly affect the composition of the surface film.

Rare Earth Based Magnesium Alloys—A Review on WE Series

“…In this sense, the intermetallic particles act as local cathodes that promote the dissolution of the neighbouring magnesium matrix, with eventual propagation of the corrosion process (Leleu et al, 2019;Soltan et al, 2019). This phenomenon has been consistently reported for WE series magnesium alloys (Coy et al, 2010;Kalb et al, 2012;Ninlachart et al, 2017;Leleu et al, 2019;Soltan et al, 2019). In contrast, it has been reported that yttrium-containing intermetallic phases have little to no effect on the corrosion process of WE magnesium alloys.…”

“…Ca and P are usually present in the surface film when the alloy is exposed to SBF (Dvorský et al, 2019). WE43 has also been tested in alkaline media containing Cl − ions, and this alloy was reported to form a passive layer composed of MgO, Mg(OH) 2 , and RE 2 O 3 phases (where REEs can be Y, Nd, or Gd) (Ninlachart et al, 2017). (Chu and Marquis, 2015) In general, it has been found that the surface films formed on WE series magnesium alloys are thinner than for pure magnesium (Zucchi et al, 2006a;Leleu et al, 2018).…”

Corrosion and Corrosion Fatigue Properties of Additively Manufactured Magnesium Alloy WE43 in Comparison to Titanium Alloy Ti-6Al-4V in Physiological Environment

“…Other studies exhibited values of i corr in a wide range between 11.9 and 409 µA/cm 2 [33,55,56] for different treatment methods of the WE43 alloy so that the results of this study (160.6 ≤ i corr ≤ 380.3 µA/cm 2 ) are within this range. The magnesium alloy WE43 is nominally a wrought material, but it is difficult to compare the corrosion properties because different treatment processes, especially heat treatments and other electrolytes, are used for these alloys [57]. Chu and Marquis determined lower values of i corr = 70 and 85 µA/cm 2 , respectively, in PDP measurements, however, in contrast to the present study, a 3.5% NaCl solution was used [58].…”

Development and In Vitro Biodegradation of Biomimetic Zwitterionic Phosphorylcholine Chitosan Coating on Zn1Mg Alloy

“…Surface treatment is the act of modifying the surface of a material by changing the physical, chemical, or biological characteristics without significantly changing the mechanical properties and chemical composition of this substrate. , In light of this feature, proper surface modification is commonly employed as an essential procedure for degradable metallic biomaterials (i.e., Fe and Mg alloys) following two basic principles, including adjusting the corrosion resistance toward the attack of ions present in the internal environment and meeting the requirement of biocompatibility . Conversion techniques (e.g., passivation, anodization, and plasma electrolytic oxidation) are comprehensively utilized for making hydr­(oxide) coatings for Mg alloys. The parameters (e.g., current/voltage density, frequency, and duty ratio) of power cell and electrolyte conditions (e.g., composition and concentration) play critical roles in determining the morphology, composition, thickness, and physiochemical/biochemical properties of the coatings.…”