*3.2. Mass-Loss Test Results*

Figure 5 shows the NAMLT results of the CR20 and CR50 alloys. The specimens were sensitized at 100 ◦C for 0, 3, 7, 48, 144, and 207 h prior to corrosion testing. The figure shows that both the CR20 and CR50 alloys had similar mass losses in concentrated nitric acid at sensitization for less than 7 h. As the sensitization time increased, the CR50 showed a slightly smaller mass-loss rate compared to the CR20 alloy. A previous study indicates that the IGC susceptibility of the Al alloys gradually decreases as the cold rolling reduction ratio increases [25].

**Figure 5.** NAMLT results of the CR20 alloy and CR50 alloy with different aging times at 100 ◦C.

The mass-loss of 25 to 75 mg/cm<sup>2</sup> indicates that the specimen is susceptible to IGC. Smaller values correspond to better corrosion resistance. The effect of the manufacturing process on the IGC of Al-Mg alloys has been previously studied [25–27]. Zhang et al. studied how the grain size modification by various manufacturing processes affected the intergranular corrosion [26]. Previous researchers reported that the NAMLT value of AA5083 alloy (~4.5 wt% of solute Mg) was 18 mg/cm<sup>2</sup> after 8 days (192 h) of sensitization exposure at 100 ◦C [27]. Similar values (19 mg/cm<sup>2</sup> after 200 h of sensitization at 100 ◦C) were obtained in the current study. Therefore, the IGC susceptibility of high Mg-containing Al-Mg alloys appears not to be negatively affected by the cold rolling process.
