Abstract
In this work, scanning electrochemical microscopy (SECM) was employed to study the corrosion behavior of anodized AZ31B magnesium alloy exposed to simulated body fluid. SECM measurements were carried out in surface generation/tip collection mode. The hydrogen evolution flux caused during corrosion of the magnesium alloy was oxidized at the ultra-microelectrode (UME). Thus, this experimental procedure allowed evaluating the effect of the anodic protection in this alloy from the SECM analysis of Z- approximation curves, cyclic voltammograms and topographic maps. The results evidence differences in the local electrochemical response of magnesium alloy in the anodized and pristine conditions. The main sites of H2 evolution were verified in the magnesium alloy without anodizing at short exposure times.
Highlights
Magnesium alloys have recently gained increasing attraction as biodegradable and biocompatible materials for resorbable medical implants
There are evidence that magnesium alloy corrosion process is initiated at heterogeneous sites in the microstructure which are mainly due to localized variations in the chemical composition of the alloy formed during the casting process[8,9]
The results indicate dynamic electrochemical activity on the AZ91D substrate at short exposure times, suggesting a rapid pit nucleation and changes in hydrogen evolution intensity[19]
Summary
Magnesium alloys have recently gained increasing attraction as biodegradable and biocompatible materials for resorbable medical implants. There are evidence that magnesium alloy corrosion process is initiated at heterogeneous sites in the microstructure which are mainly due to localized variations in the chemical composition of the alloy formed during the casting process[8,9]. Several works showed that one of the simplest and most effective methods for studying the corrosion rates of magnesium in aqueous solutions is by measuring hydrogen gas evolution associated with the magnesium corrosion process as shown in Eq (1)[10,11,12,13]. Magnesium and its alloys produce magnesium hydroxide (Mg (OH)2) and molecular hydrogen (H2) when are exposed to aqueous environments, where the main cathodic reaction is water reduction, with hydrogen evolution and local alkalization, as shown in Eqs. Magnesium and its alloys produce magnesium hydroxide (Mg (OH)2) and molecular hydrogen (H2) when are exposed to aqueous environments, where the main cathodic reaction is water reduction, with hydrogen evolution and local alkalization, as shown in Eqs. (2) to (4)[14,15]
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