Official Answer
Answer
Galvanic corrosion occurs when the retaining ring (e.g., 17-7PH) is in electrical contact with a more noble or less noble housing material (e.g., Titanium or Carbon Steel) in an electrolyte (seawater). If the ring is the anode, it will corrode rapidly, leading to a loss of cross-sectional area and thrust capacity. If the ring is the cathode, it may be subject to Hydrogen Induced Stress Cracking (HISC) due to the hydrogen generated by the cathodic protection system. Analysis involves checking the 'Galvanic Series' and ensuring that the potential difference $\Delta V < 0.2V$ or that appropriate coatings/isolation are used.
