This study investigates the corrosion resistance of a hard anodized aluminum joint enclosure used in an underwater robotic arm. An accelerated corrosion test, based on Arrhenius equation, is designed to simulate 10,000 h of operational exposure in North Sea conditions (salinity 38 ppt, seawater typical temperature 15 °C) within 1,043 h by increasing simulated seawater temperature (50 °C). A sacrificial magnesium anode is applied to provide cathodic protection against galvanic corrosion to critical areas where are exposed directly to the seawater. Throughout the test, comprehensive insights, including visual inspections, weight measurements, and vacuum pressure evaluations, are conducted to monitor corrosion effects on the joint enclosure surface and ensure sealing performance. This vacuum pressure test methodology provides a non-destructive, quantitative assessment of the integrity of the joint enclosure before and after corrosion testing, which offers insight into the corrosion resistance and functional reliability of the joint. The results confirm that the joint enclosure performs high corrosion resistance and reliable sealing under operational marine environment, validating the effectiveness of accelerated test for corrosion evaluation. Additionally, practical recommendations are proposed to enhance the corrosion resistance and sealing performance of the joint enclosure.