JMullison
Marine/Ocean
- Jul 29, 2003
- 1
Hello All,
This concerns a pressure case made from 7075 Aluminum and anodized to the following spec: 'MIL-A-8625 Type III, Class 1 including duplex seal on all components, 0.001" buildup/0.02" thick'. This case is several years old, and has pressure cycled in the ocean to several thousand meters a few hundred times.
On the contact surfaces exposed to saltwater, that is, the mating surfaces on the high pressure side of the o-ring, it has started to show extensive bubbling. The bubbles range from one to several millimeters, and they chip off fairly easily, some can be simply rubbed off with a fingertip to expose the bare aluminum. The exposed aluminum does not look (to the naked eye) to be heavily corroded.
Is this sort of failure something I should expect to see given the operating envelope for the pressure case? Can someone help me with a cause of what might be happening here? From reading similar posts I see that impurities in the aluminum may be the culprit, but those seem to have shown problems earlier than I am seeing here. Could the pressure cycling be a factor?
Thanks in advance for your help.
This concerns a pressure case made from 7075 Aluminum and anodized to the following spec: 'MIL-A-8625 Type III, Class 1 including duplex seal on all components, 0.001" buildup/0.02" thick'. This case is several years old, and has pressure cycled in the ocean to several thousand meters a few hundred times.
On the contact surfaces exposed to saltwater, that is, the mating surfaces on the high pressure side of the o-ring, it has started to show extensive bubbling. The bubbles range from one to several millimeters, and they chip off fairly easily, some can be simply rubbed off with a fingertip to expose the bare aluminum. The exposed aluminum does not look (to the naked eye) to be heavily corroded.
Is this sort of failure something I should expect to see given the operating envelope for the pressure case? Can someone help me with a cause of what might be happening here? From reading similar posts I see that impurities in the aluminum may be the culprit, but those seem to have shown problems earlier than I am seeing here. Could the pressure cycling be a factor?
Thanks in advance for your help.
