Official Answer
Answer
While both are austenitic stainless steels, $316$ Stainless Steel contains $2-3\%$ Molybdenum ($Mo$), which significantly enhances its resistance to 'pitting' and 'crevice corrosion' in chloride-rich environments (like seawater). $302$ Stainless Steel is more susceptible to localized attack. However, $302$ can be cold-worked to higher tensile strengths ($>200$ ksi) than $316$ ($>160$ ksi), meaning a $302$ ring can hold higher thrust loads for the same size. For marine applications, if the load is moderate, $316$ is preferred. If high load is required, a $302$ ring with a 'Passivation' treatment (per ASTM A967) or a 'Black Oxide' finish may be used, though $17-7PH$ is often the better compromise for both strength and corrosion resistance.
