Well, for sure increasing the partial pressure will decrease the pH as the solubility will increase. However, from corrosion point the pH is a strong factor as it complete the electrochemical reaction. the low pH indicates the high H+ in the stream, which will act as cathodic reaction.
maybe...
Referring to NACE SP040315, At 100 C and lower you are safe. However, it also mention that 30 C margin below the delayed SCC shall be applied to avoid localized caustic concentration and delayed cracking. I think if it only for few hours, than you're fine.
pH of 6.7 is very low for water service that indicates the presence of acids (either high CO2 & Chloride)
as per API 581 Carbon dioxide corrosion table, corrosion rate can be as high as 0.9 to 1.02 mm/y at pH of 6.5 & temperature of 40 - 80 C.
Normally, for water service, pH target is above 8
3000 ppm is too high for 316, as per ASM, the maximum 316 can withstand is 1000 ppm for pitting corrosion at ambient temp, this limit decreases as temperature increase.
Also, for the presence of welding and to avoid Cl-SCC, API 581 shift the cracking susceptibility from medium to high as...
