To protect workers against falling from heights in a professional environment, lifelines are used. These lifelines are typically made from stainless steel to ensure excellent performance in an industrial environment.
An industrial stainless steel lifeline showed early breakdown after less than 18 months of service. To analyse this early breakdown, OCAS sampled and investigated the lifeline.
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Microscopic observation revealed the presence of pitting as well as stress corrosion cracking in the failed area of the lifeline.
Analysis using Electron Probe Micro Analyser equipped with energy dispersive X-ray detection (EPMA-EDX) confirmed the presence of chlorides in the cracked area.
The lifeline was in use in an environment of high relative humidity showing considerable concentrations of chlorides. The combination of the presence of chlorides on the surface and the tension of the lifeline, prevents the renewal of the thin protective layer of chromiumoxide, typical for stainless steel. As a result, the simultaneous action of a corrodent (chloride) and sustained tensile stress triggers stress corrosion cracking. These conditions typically occur in swimming pool structures and industrial areas.
For safety reasons, a lifeline should always remain under tension. It was furthermore not possible to prevent contact with chlorides by rinsing or isolating the lifeline. Therefore, OCAS recommended to use another material for the lifeline.
“Chloride stress corrosion cracking can cause serious issues.”