PSI - Issue 42

A. Laureys et al. / Procedia Structural Integrity 42 (2022) 1458–1466 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

1462

5

100 C

120 C

140 C

160 C

100 C

100 C

120 C

80 C

25 µm

25 µm

25 µm

Figure 2. SEM images of corroded 316L surface after testing for 48 h in 85 wt% FGPA at various temperatures.

130 C

C

160 C

Precipitates 120 C

100 C

160 C

140 C

25 µm

25 µm

25 µm

Figure 3. SEM images of corroded 316Ti surface after testing for 48 h in 85 wt% FGPA at various temperatures. Fig. 4 shows that below temperatures of 110 °C Sanicro28 only experiences limited corrosion in 85 wt% FGPA. Breakthrough of the passive film occurs around 110 °C. At 120 °C the surface is etched by uniform corrosion and some local attack is observed, while at temperatures starting from 140 °C the material corrodes significantly. The surface is severely affected by corrosion and the etched surface is completely consumed. Local corrosion damage found on 316L and Sanicro28 exhibited a specific geometry, i.e. triangular and square indents (e.g. Sanicro28 tested at 120 °C in Fig. 4). Analysis of the pits on Sanicro28 shows that the orientation of the pits depends on the crystallographic orientation of the grains in which they form. 160 C 100 C 110 C 10 C 1 0 C 100 C

120 C

120 C

C

140 C

160 C

160 C

170 C

170 C

1 0 C

110 C

140 C

140 C

120 C

120 C

25 µm

25 µm

25 µm

25 µm

Figure 4. SEM images of corroded Sanicro28 surface after testing for 48 h in 85 wt% FGPA at various temperatures . Fig. 5 illustrates the surface of Sanicro35 after testing in 85 wt% FGPA for 48 h at various temperatures. Sanicro35 does not show significant corrosion at reaction temperatures below 120 °C. Uniform corrosion and minor local attack were observed at 120, 130 and 140 °C. Beyond 140 °C severe corrosion of the surface was observed and the surface was consumed by corrosion, which also corresponds with a strong increase in corrosion rate (Fig. 1). Even at 160 °C some of the etched surface is still found. Up to 140 °C Sanicro35 shows a better resistance to local corrosion than Sanicro28 and 316L and 316Ti. 160 C 170 C 160 C 170 C