This specification covers high magnesium marine application aluminum-alloy in those alloy tempers for flat sheet, coiled sheet, and plate, in the mill finish that are intended for marine and similar environments. An inspection lot shall consist of an identifiable quantity of material of the same mill form, alloy, temper, cast or melt lot, and thickness, subjected to inspection at one time. The material shall be supplied in the mill finish and shall be uniform as defined by the requirements of this specification and shall be commercially sound. Each coil, sheet and plate shall be examined to determine conformance to this specification with respect to general quality and identification marking. One sample shall be taken from each end of each parent coil, or parent plate. Alloy-tempers are manufactured and corrosion tested for intended use in marine hull construction or in marine applications where frequent or constant direct contact with seawater is expected. The specimen shall be capable of exhibiting resistance to intergranular corrosion as indicated by an acceptable mass-loss when tested and shall also be capable of exhibiting no evidence of exfoliation or corrosion. Under metallographic examination, the microstructure of a sample from each production lot shall be compared to that of the producer-established reference photomicrograph of acceptable material, in the same thickness range. Each shipping container shall be marked with the purchase order number, material size, specification number, alloy and temper, gross and net weights, and the producer's name or trademark.