Water Quality Effects During Hydrostatic-Testing on Corrosion Behavior of AISI 316L Austenitic Stainless Steel Piping

Potential corrosion problems associated with hydrotesting AISI 316L austenitic stainless steel piping are addressed. Newly constructed pipelines or ones that are repaired must be subjected to hydrostatic-test for strength and leak check to prove the structural integrity of the piping. One of the suspected drawbacks associated with hydrostatic-testing is the existence of long-term problems that can eventually lead to costly failures. A common problem is the development of microbiological influenced corrosion (MIC). The variables that were evaluated include the solution pH, chloride concentration [Cl^-], the effect of oxygen presence and the influence of microorganisms on corrosion behavior. It was clearly evident that as chloride concentration increases the passivity of the metal decreases. The absence of oxygen increases the passive range and decreases the difference between pitting potential (E_pit) and protection potential (E_prot) but shifts corrosion potential (E_corr) to more active potentials. Ennoblement was observed after the development of biofilm on metal surface. The results show the importance of setting proper water quality parameters to avoid long-term corrosion problems.