Failure modes water oxidation

A more dramatic failure results in peel strengths of 0-10 g/mm and is characterized as an adhesive failure at the polyimide/metal oxide interface.This was the only failure mode observed in Ti and Zr films. Isotopically tagged water used with SIMS analysis shows that on annealing water reacts with the Ti with oxygen segregating to the metal/polyimide interface and hydrogen penetrating into the bulk of the Ti, in these samples. 

Another kind of corrosion sustained by medical implants is the metal-ion oxidation sustained by polyurethane pacemaker leads. This failure mode is highly complex and involves water transport across the insulation of the lead, allowing contact with the Co-Cr alloy, which then corrodes by a fretting mechanism. The metal ions, in particular Co +, then penetrate the polyurethane and oxidize it in a catalytic fashion. This leads ultimately to an electrical breach in the lead and failure of the pacemaker, often resulting in the death of the patient. 

By replacing water as the exterior medium with air, embrittlement occurs after just 20,000 h. Fracture is initiated at degraded, oxidized areas in the pipe wall. These oxidized areas (that occur only in polyolefin pipe) are discolored and covered by cracks, illustrating the degree of embrittlement. The brittle failure mode of crosslinked polyethylene pipe with less than 68% gel content is Stage 2 failure. 

To address the problem of the failure mode of the concrete cylinder, a double crucible of siliceous concrete was used in the BETA facility (figure 2). Inner and outer crucible form an annulus which is filled with water to a level corresponding to 350 mm above the initial bottom of the inner crucible. The inner crucible with a wall thickness of 100 mm towards the water annulus, has 380 mm inner diameter and is filled with the metallic and oxidic melt, eroding the concrete. The outer crucible has a wall thickness of 150 mm, outer diameter 1080 mm. 

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