What causes sulfide stress cracking?
Sulfide stress cracking (SSC) occurs when atomic hydrogen diffuses into the metal but remains in solid solution in the crystal lattice. This reduces the ductility and deformability of the metal, which is termed hydrogen embrittlement.
How do you prevent sulphide stress cracking?
Sulfide Stress Cracking can be prevented through:
- Control of stress level (residual or load) and hardness.
- Apply post-weld heat treatment (PWHT). Computer software ACE – Apps for Corrosion Engineers has a module to determine when PWHT or Pre-Heating is required.
- Avoid the hydrogen source.
What is sulfide stress cracking test?
SSC (Sulfide Stress Cracking Test) Test standards describe many different procedures to simulate and evaluate the reaction of the material to the double effect of mechanical strenght and corrosion attack. Various H2S solutions and chloride content solutions may be used to simulate sour environments.
What causes hydrogen embrittlement in steel?
Hydrogen Embrittlement occurs when metals become brittle as a result of the introduction and diffusion of hydrogen into the material. The degree of embrittlement is influenced both by the amount of hydrogen absorbed and the microstructure of the material.
What causes hydrogen induced cracking?
When such hydrogen atoms combine again in very small metal voids to build molecules of hydrogen, they produce pressure within the cavity. The pressure created from the buildup can further elevate, which makes metal lose its tensile strength and ductility, reaching the point of cracking, or HIC.
How do you prevent hydrogen induced cracking?
Hydrogen-induced cracking can be prevented through:
- Control of stress level (residual or load) and hardness. Computer software H2Compass can be used to determine when PWHT or Pre-Heating is required. Click here for details on the H2Compass software.
- Avoid the hydrogen source.
- Baking to remove hydrogen.
What causes stress corrosion cracking in stainless steel?
The combination of tensile stress and a specific corrosive environment can crack stainless steels. This mode of attack is termed stress corrosion cracking (SCC). The most common environmental exposure condition responsible for SCC of stainless steels is the presence of chlorides.
Why HIC testing is required?
Element offers Hydrogen Induced Cracking (HIC) tests to accurately assess the susceptibility of your carbon and low alloy steel equipment to hydrogen induced cracking in wet H2S/sour service operating environments such as in the Oil & Gas industry. The tests are normally carried out according to NACE TM0284.
How does hydrogen affect steel?
Hydrogen gas can adsorb and dissociate on the steel surface to produce atomic hydrogen. 2,3 The subsequent dissolution and diffusion of atomic hydrogen into steels can degrade mechanical properties, a phenomenon generally referred to as hydrogen embrittlement.
What causes steel to crack?
Steel can fracture rapidly at low temperature and can crack during welding, in fatigue or as a result of stress corrosion. Certain fabrication processes such as welding, flame cutting and punching exacerbate the risks, especially if the steel is ‘thick’. Galvanising can also be a risk factor.
Does hydrogen react with steel?
How do you prevent hydrogen embrittlement?
Preventing hydrogen embrittlement Baking metals is a common means of removing hydrogen during the manufacturing process as is avoiding quick changes in temperature that might lead to condensation.