Corrosion of NiTiDiscs in Different Seawater Environments

Abstract

This paper gives an approach to the corrosion resistance analysis and changes in the chemical composition of anNiTi alloy in the shape of a disc, depending on different real seawater environments. The NiTi discs were analysed after 6 months of exposure in real seawater environments: the atmosphere, a tidal zone, and seawater. The corrosion tests showed that the highest corrosion rate for the discs is in seawater because this had the highest value of current density, and the initial disc had the most negative potential. Measuring the chemical composition of the discs using inductively coupled plasma and X-ray fluorescence before the experiment and semiquantitative analysis after the experiment showed the chemical composition after 6 months of exposure. Furthermore, the applied principal component analysis and cluster analysis revealed the influence of the different environments on the changes in the chemical composition of the discs. Cluster analysis detected small differences between the similar corrosive influences of the analysed types of environments during the period of exposure. The obtained results confirm that PCA can detect subtle quantitative differences among the corrosive influences of the types of marine environments, although the examined corrosive influences are quite similar. The applied chemometric methods (CA and PCA) are, therefore, sensitive enough to register the existence of slight differences among corrosive environmental influences on the analysed NiTi SMA.

Chemometrics as a tool for monitoring corrosion degradation of the selected alloys in real conditions

“…The alloy surfaces were covered with a mixture of corrosion products and deposited inorganic salts (Figure S1 and Table S1). 13,19 During this period, organic deposition and pitting corrosion were not detected on the NiTi surface 20,21 …”

“…In our previous work, we investigated the corrosion behavior of the NiTi alloy, which has the same chemical compositions as the one examined in this manuscript, with the difference that it was produced by different technological production processes, more precisely by classical casting 19 …”

“…The alloy surfaces were covered with a mixture of corrosion products and deposited inorganic salts (Figure S1 and Table S1). 13,19 During this period, organic deposition and pitting corrosion were not detected on the NiTi surface. 20,21 Figure 1 shows the metal content (Ni and Ti) obtained by EDS analysis after 6 months exposure in the tested marine environments.…”

“…In our previous work, we investigated the corrosion behavior of the NiTi alloy, which has the same chemical compositions as the one examined in this manuscript, with the difference that it was produced by different technological production processes, more precisely by classical casting. 19 In order to verify whether different manufacturing production processes affect the corrosion behavior of the NiTi alloy in the tested marine environments, the EDS results obtained for both alloys at an exposure period of 6 months were collected in one matrix for PCA in the same way as was described earlier.…”