What Does Hydrogen Stress Cracking Mean?
Hydrogen stress cracking occurs when hydrogen penetrates high-strength or hardened metal in a state of tensile stress. While these metals may normally be ductile in nature, the presence of hydrogen in a corroded environment can cause it to crack. These cracks, if undetected, can lead to failure of the pipeline.
Trenchless rehabilitation methods for sewer repair have made it possible to detect and repair these problems before failure occurs.
Trenchlesspedia Explains Hydrogen Stress Cracking
Hydrogen stress cracking affects different types of high-strength metals such as low alloy steels and high-strength carbon. These metals sometimes have areas that have hardened due to excess amount of residual elements, especially near welded zones. If a crack already exists in the weld, the stress cracking will begin near the crack because hydrogen is attracted to regions under stress. The hydrogen then assists in fracturing the metal further.
This type of cracking, however, occurs mostly at the surface, and thus, is easy to find. Hydrogen stress cracking can be prevented by treating welded components post weld at high temperatures to reduce hardness and strength of weldments, and by reducing the tensile stress of the component itself.