ISO 15156-3:2015 gives requirements and recommendations for the selection and qualification of CRAs (corrosion-resistant alloys) and other alloys for service in equipment used in oil and natural gas production and natural gas treatment plants in H2S-containing environments whose failure can pose a risk to the health and safety of the public and personnel or to the environment. It can be applied to help avoid costly corrosion damage to the equipment itself. It supplements, but does not replace, the materials requirements of the appropriate design codes, standards, or regulations.ISO 15156-3:2015 addresses the resistance of these materials to damage that can be caused by sulfide stress-cracking (SSC), stress-corrosion cracking (SCC), and galvanically induced hydrogen stress cracking (GHSC).ISO 15156-3:2015 is concerned only with cracking. Loss of material by general (mass loss) or localized corrosion is not addressed.Table 1 provides a non-exhaustive list of equipment to which this part of ISO 15156 is applicable, including permitted exclusions.ISO 15156-3:2015 applies to the qualification and selection of materials for equipment designed and constructed using load controlled design methods. For design utilizing strain-based design methods, see ISO 15156-1:2015, Clause 5.ISO 15156-3:2015 is not necessarily suitable for application to equipment used in refining or downstream processes and equipment.