Which material must use low-chloride hydrotest water and be drained after hydrotest?

Which material must use low-chloride hydrotest water and be drained after hydrotest?

• A. Aluminum
• B. 300 series Stainless Steel
• C. Monel
• D. Carbon Steel

Answer: (B)

Chloride-induced stress corrosion cracking risk in 300-series stainless steel during hydrotesting drives the requirement for low-chloride hydrotest water and draining afterward. The austenitic stainless steels in this group rely on a protective chromium oxide film, but chloride ions can penetrate and destabilize that passive layer, especially when the metal is under the tensile stress of pressurized testing. Using water with very low chloride content minimizes those ions, reducing the chance of cracking during the test. After the test, draining the water removes residual chlorides and moisture, preventing ongoing exposure that could promote corrosion or cracking as the system cools and dries. Other materials like carbon steel, aluminum, or Monel don’t have the same SCC concern from chlorides during hydrotesting, so the low-chloride requirement and mandatory drainage are specifically linked to the stainless steel type mentioned.

Chloride-induced stress corrosion cracking risk in 300-series stainless steel during hydrotesting drives the requirement for low-chloride hydrotest water and draining afterward. The austenitic stainless steels in this group rely on a protective chromium oxide film, but chloride ions can penetrate and destabilize that passive layer, especially when the metal is under the tensile stress of pressurized testing. Using water with very low chloride content minimizes those ions, reducing the chance of cracking during the test. After the test, draining the water removes residual chlorides and moisture, preventing ongoing exposure that could promote corrosion or cracking as the system cools and dries. Other materials like carbon steel, aluminum, or Monel don’t have the same SCC concern from chlorides during hydrotesting, so the low-chloride requirement and mandatory drainage are specifically linked to the stainless steel type mentioned.