Our SSC Test measures stress corrosion cracking in solutions with hydrogen sulfide (H2S). Contact between hydrogen sulfide and steel leads to crack development through the phenomenon known as Sulphide Stress Cracking (SSC) or Sulphide Stress Corrosion Cracking (SSCC). These terms indicate the formation of cracks perpendicular to the material surface caused by contact with H2S in the presence of mechanical stresses, giving rise to a particular form of environmental corrosion known as stress corrosion cracking.

Main standards used

The phenomenon of SSC can be studied through different methods codified by NACE and EFC. The main reference standards include:

• NACE TM0177
• NACE TM0316
• EFC 16

The solutions used in the tests contain sodium chloride, acetic acid and/or sodium acetate in varying proportions, according to reference standards. These solutions are saturated with hydrogen sulfide (H2S), and specimens are tensioned and immersed in these solutions to simulate the actual environments with which the materials will come into contact.

Testing techniques

• Four Point Bending (FPB)
  One of the most common methods is Four Point Bending (FPB), often requested as NACE TM0316, NACE TM0177 + ASTM G39 or EFC 16 Method B. This method uses a tensioned parallelepiped specimen with four points of contact, where the stress is concentrated between the two internal rollers.
  The load can be applied by digital comparator or by strain gauge installation.
• Proof Ring
  When it is necessary to apply stress oriented in a specific direction, we use the Proof Ring method, often requested as SSC Test NACE TM0177 or EFC 16 Method A. This test involves a specimen similar to a tensile test, loaded with uniaxial stress and immersed in a dedicated cell to maintain the required environmental conditions.

Test duration and analysis

Regardless of the method used, the test has a duration of 720 hours. At the end of the test, the stressed area is analyzed to determine the presence of typical SSC cracks.

Corrosion from Sour Service and CRA.

Stress corrosion occurs from the combination of an applied stress and a corrosive environment saturated with H2S. This type of corrosion is known as SSC or SSCC when it occurs at room temperature, mainly on carbon and low-alloy steels. On stainless steels, duplex or CRA, it is called Stress Corrosion Cracking (SCC).

The danger of stress corrosion cracking for materials used in the petroleum industry has been known since the 1950s. Regulations such as MR0175/ISO15156 facilitate the selection of materials resistant to H2S and stress corrosion cracking phenomena.