Multi-Scale Monitoring the First Stages of Electrochemical Behavior of AZ31B Magnesium Alloy in Simulated Body Fluid

Abstract

This work applies electrochemical noise technique (EN) and scanning electrochemical microscopy (SECM) to investigate the initial stages of degradation of AZ31B magnesium alloy in simulated body fluid (SBF). The fluctuations in potential and current, caused by the alloy's spontaneous degradation, were analyzed in both time and frequency domains to determine the type of attack and the fractal nature of the degradation. Substrate-generation/tip-collection mode SECM mapped the hydrogen evolution activity at the Mg surface during the initial corrosion process. This electrochemical information was correlated with pH changes of the solution, Mg ion concentration, mass loss, SEM-EDS and XPS analysis. The Mg matrix dissolution was promoted by Al-Mn intermetallic particles, which acted as cathodic sites. The corrosion products film was mainly composed by Mg(OH) 2 and Ca 10 (PO 4 ) 6 (OH) 2 , and its fast formation allowed a slower degradation and H 2 evolution rates. Combining EN and SECM methods allowed the description of the early degradation processes of AZ31B in SBF as a persistent stationary process, related to fractional Gaussian noise, which was characterized by the quasi-uniform corrosion of the alloy.

Initial Stages of AZ31B Magnesium Alloy Degradation in Ringer’s Solution: Interpretation of EIS, Mass Loss, Hydrogen Evolution Data and Scanning Electron Microscopy Observations

“…Cathodically active intermetallic Al-Mn particles located within the grains of α-Mg matrix are the main second phase constituents of AZ31B microstructure, such as Al 8 Mn 5 , ε-AlMn, Al 11 Mn 4 and β-Mn(Al) [21][22][23][24][25]. The corrosion mechanism directly depends on their distribution and the solution composition [26][27][28][29][30][31][32]. As test media in this work was selected Ringer's solution, which is an isotonic (physiological) aqueous solution of NaCl with additional compounds, as found in human body fluids (blood serum).…”

The Application of Electrochemical Noise for the Study of Metal Corrosion and Organic Anticorrosion Coatings: A Review

“…The values of β exponent in PSD graphs suggest that corrosion process of AA2219‐T42 alloy occurs as a persistent non‐stationary process, the dynamics of which is controlled by fractional Brownian motion (fBm), while on AA6061‐T6 alloy the corrosion process was dominated by stationary and weakly persistent features, with the contribution of fractional Gaussian noise (fGn). In terms of magnesium alloys, E. Mena‐Morcillo applied electrochemical noise technique to investigate the initial stages of degradation of AZ31B magnesium alloy in simulated body fluid [46] . The fluctuations in potential and current, caused by the alloy‘s spontaneous degradation, were analyzed in both time and frequency domains to determine the type of attack and the fractal nature of the degradation.…”

“…In terms of magnesium alloys, E. Mena-Morcillo applied electrochemical noise technique to investigate the initial stages of degradation of AZ31B magnesium alloy in simulated body fluid. [46] The fluctuations in potential and current, caused by the alloy's spontaneous degradation, were analyzed in both time and frequency domains to determine the type of attack and the fractal nature of the degradation. The studies allowed the description of the early degradation processes of AZ31B in simulated body fluid as a persistent stationary process, related to fractional Gaussian noise, which was characterized by the quasi-uniform corrosion of the alloy.…”

Effect of Laminar Flow on the Corrosion Activity of AA6061-T6 in Seawater

“…The β exponent is a parameter correlated with the strength of persistence in a process [26]. In our previous studies, EN technique was carried out to characterise the first stages of corrosion in stationary seawater of copper [27], aluminium [28] and aluminium alloys [29], as well as the initial stages of AZ31B Mg alloy in simulated body fluid [30].…”