R. G. Baggerly, Associate of MDE, Anacortes, WA; R. K. Kent, MDE Engineers Inc., Seattle, WA
Aluminum has been used successfully for many years in the boat building industry with the Al-Mg alloy system being of major importance. These alloys are readily weldable and provide good corrosion resistance as well as adequate strength. However, with increasing magnesium content the alloy may develop sensitization in the grain boundaries and become susceptible to stress corrosion cracking. The sheet and plate of these alloys can be processed thermally to immunize them from this condition. In very recent history, a problem developed in the Pacific Northwest where 5083 aluminum alloy was being used for welded boat construction and stress corrosion cracks developed within months of being placed in marine service. This presentation will discuss failures in new boats, a particular temper designation for this alloy that should not have been used in the marine industry, the tests conducted and some metallurgical history for this alloy.
Summary: Aluminum has been used successfully for many years in the boat building industry with the Al-Mg alloy system being of major importance. These alloys are readily weldable and provide good corrosion resistance as well as adequate strength. However, with increasing magnesium content the alloy may develop sensitization in the grain boundaries and become susceptible to stress corrosion cracking. The sheet and plate of these alloys can be processed thermally to immunize them from this condition. In very recent history, a problem developed in the Pacific Northwest where 5083 aluminum alloy was being used for welded boat construction and stress corrosion cracks developed within months of being placed in marine service. This presentation will discuss failures in new boats, a particular temper designation for this alloy that should not have been used in the marine industry, the tests conducted and some metallurgical history for this alloy.
