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Taking into account the background information on intergranular corrosion of aluminum alloys mentioned earlier, the aluminum alloy series that are less prone to intergranular corrosion include the following categories: First, Series 1 (pure aluminum series). Composition characteristics: The total proportion of alloying elements is extremely low; it contains almost no elements such as copper and zinc, which can cause intergranular potential differences. Corrosion resistance: It is the series with the best intergranular corrosion resistance among all wrought aluminum alloys; intergranular corrosion hardly occurs under normal operating conditions. II. Series 3 (Al-Mn series rust-resistant aluminum alloys): Characterized by manganese as the main alloying element, with no negatively charged phases that tend to precipitate continuously at the grain boundaries. Corrosion resistance: It belongs to the category of classic rust-resistant aluminum alloys, with extremely low sensitivity to intergranular corrosion; it is widely used in applications such as radiators and tanks where high corrosion resistance is required. III. Composition characteristics of 5-series (Al-Mg series) aluminum alloys in normal conditions: The magnesium content is ≤3%, and no stress-induced heat treatment is applied; as a result, no continuous β-phase network forms at the grain boundaries. Corrosion resistance: It exhibits excellent intergranular corrosion resistance under normal service conditions, making it a commonly used corrosion-resistant aluminum alloy in marine engineering. Additional note: Series 6 aluminum alloys are less prone to intergranular corrosion only under special conditions where the heat treatment process is fully compliant and the copper content is extremely low; conventional mass-produced grades still require an assessment of their susceptibility to intergranular corrosion ； Aluminum alloys of series 2 and 7 belong to the highly sensitive category, and it is almost impossible to completely eliminate the risk of intergranular corrosion using conventional processing methods.