The nickel-based alloys UNS N06625 and N08825 are today commonly used in the Oil & Gas industry for piping or pressure vessels applications. The material selection is mainly driven by the corrosivity of the environment in terms of chloride concentration, temperature, pH and H2S partial pressure. For these applications, several mechanical characteristics are generally required. Clad plates represent therefore a cost-effective solution, combining the corrosion resistance of a nickel alloy layer (thickness around 3 mm - 1/8 inch) to the mechanical properties of a carbon-steel backer material.
This paper will be dedicated to the corrosion resistance of roll-bonded UNS N06625 and N08825 clad materials. Special attention will be paid to their resistance to stress corrosion cracking which is the primary cracking mechanism that shall be considered for nickel alloys as per NACE MR 0175 / ISO 15156 part 3. Results regarding their pitting corrosion and intergranular corrosion resistance will also be provided.
Keywords: UNS N08825, UNS N06625, roll-bonded cladding, PWHT, sensitization, standard corrosion tests, stress corrosion cracking