0.0225
3.83
Corrosion rate (mm/yr) pH (Y2)
0.0220
3.73
0.0215
3.63
0.0210
0.0205
3.53
0.0200
3.43
0.0195
3.33
0.0190
Temperature (˚C)
Figure 3 HEX 06 outlet to HEX 07 outlet – corrosion rate – SS316 L
Corrosion is calculated by quantifying the bulk chemis- try, transport phenomena, and surface reactions through a thermophysical and electrochemical module. Figures 2-4 show the results of the corrosion risk assessment carried out for the 10% POME incorporation rate case: HEX 06 to HEX 07 uniform corrosion risk assessment for carbon steel (see Figure 2 ), stainless steel SS316L (see Figure 3 ), and Hastelloy C-276 (see Figure 4 ). It is evident that the corrosion rate exceeds the accept- able limits for long-term continuous service for carbon steel material. Therefore, chloride stress corrosion cracking (CSCC) becomes the predominant damage mechanism. As a result, the MoC for tube bundles and piping systems should be upgraded to SS316L or Hastelloy C-276. Localised corrosion risk Using the proprietary Corrosion Analyser, it is also possible to calculate the localised corrosion risk of alloys by deter- mining the corrosion and re-passivation potential: • Corrosion potential (E corr ): Electric potential where anodic reaction rates = cathodic reaction rates. This results in no net current flowing into or out of the electrode. This poten - tial determines the likelihood of metal corrosion in the
specified environment. Consider this potential as the inher - ent tendency of a material to corrode. • Repassivation potential (E rp ): Also called the protection potential, the E rp is the potential at which a stably grow- ing pit or crevice corrosion will cease to grow. At potentials below E rp , localised corrosion is unable to progress. It can Corrosion is calculated by quantifying the bulk chemistry, transport phenomena, and surface reactions through a thermophysical and electrochemical module
be considered the threshold needed for a pit or crevice to cease its corrosion activity. The wider the E corr – E rp difference, the greater the pro- pensity for localised corrosion. This delta is referred to as the Maximum Pit Current Density and is measured in A/m²,
0.001232
3.83
Corrosion rate (mm/yr) pH (Y2)
0.001222
3.73
0.001212
0.001202
3.63
0.001192
3.53
0.001182
0.001172
3.43
0.001162
3.33
0.001152
Temperature (˚C)
Figure 4 HEX 06 outlet to HEX 07 outlet – corrosion rate – Hastelloy C-276
43
PTQ Q3 2024
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