Real-time dissolution of a compositionally complex alloy using inline ICP and correlation with XPS

Abstract

The real-time dissolution of the single-phase compositionally complex alloy (CCA), Al1.5TiVCr, was studied using an inline inductively coupled plasma method. Compositionally complex alloys (CCAs), a term encompassing high entropy alloys (HEAs) or multi-principal element alloys (MPEAs), are -in general -noted for their inherently high corrosion resistance. In order to gain an insight into the dissolution of Al1.5TiVCr alloy, atomic emission spectroelectrochemistry was utilised in order to measure the ion dissolution of the alloy during anodic polarisation. It was revealed that incongruent dissolution occurred, with preferential dissolution of Al, and essentially no dissolution of Ti, until the point of alloy breakdown. Results were correlated with X-ray photoelectron spectroscopy, which revealed a complex surface oxide inclusive of unoxidised metal, and metal oxides in disproportion to the bulk alloying element ratio.

Recent insights in corrosion science from atomic spectroelectrochemistry

“…[ 86 ] However, in spite of the single‐phase structure of Al1.5TiVCr, selective dissolution of Al was reported at OCP and during anodic polarisation on 0.1 M NaCl. [ 87 ] This confirmed that Al 2 O 3 is less resilient to chloride than the oxide of Cr, Ti, and V. The dissolution rate of Al was found to decrease with increasing fractions of Cr (III), Ti(IV), and V(III) oxides in the passive film of AlTiVCr. Moreover, the presence of Ti was seen to inhibit the transpassive dissolution potential of V and Cr.…”

“…Apart from conventional alloys, most multi‐principal element alloys studied using ASEC are found to dissolve incongruently. [ 85–91 ] Evolution of dissolution rate of each alloying element from alloys is found to depend on applied potential, exposure duration, pH, and so on. For example, both pH and exposure duration influenced the dissolution ratios of $$\frac{{{{{\upsilon}}_{Zn}}}}{{{{{\upsilon}}_{Al}}}}$$ in Al‐Zn alloys, [ 72 ] $$\frac{{{{{\upsilon}}_{Mg}}}}{{{{{\upsilon}}_{Si}}}}$$ in Mg 2 Si.…”

“…Apart from conventional alloys, most multi-principal element alloys studied using ASEC are found to dissolve incongruently. [85][86][87][88][89][90][91] Evolution of dissolution rate of each alloying element from alloys is found to depend on applied potential, exposure duration, pH, and so on. For example, both pH and exposure duration influenced the dissolution ratios of…”

“…A few passive MPEAs are found to dissolve significantly in the OER region during anodic polarisation. [87][88][89] In such cases, dissolution behavior was incongruent, suggesting dissimilar responses of different oxides (present in the surface film of alloys) to oxygen evolution. In contrast to the systems mentioned above, the dissolution rate of Ti slightly decrease and remained independent of applied anodic potential during oxygen evolution in 0.1 M H 2 SO 4 .…”

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“…Thus, it has to be understood that the term MPEAs includes both HEAs and MEAs, having composition of base elements in relatively larger proportion. Recently, a broader term compositionally complex alloys (CCA) has been coined to represent MPEAs [9].…”