Corrosion testing continued stainless steel

A dense and electronically insulating layer of LiA102 is not suitable for providing corrosion resistance to the cell current collectors because these components must remain electrically conductive. The typical materials used for this application are 316 stainless steel and chromium plated stainless steels. However, materials with better corrosion resistance are required for longterm operation of MCFCs. Research is continuing to understand the corrosion processes of chromium in molten carbonate salts under both fuel gas and oxidizing gas environments (23,25) and to identify improved alloys (29) for MCFCs. Stainless steels such as Type 310 and 446 have demonstrated better corrosion resistance than Type 316 in corrosion tests (29). 

The cone calorimeter is also used to quantify the corrosivity of products of combustion as described in ASTM D 5485. The Cone Corrosimeter uses the same load cell, specimen holder, retainer frame, spark igniter, conical heater, and exhaust system as the cone calorimeter. A heated stainless steel sampling tube is connected to a funnel placed on top of the conical heater. A gas sample is continuously drawn from the tube at a rate of 4.5 L/min. The sampling tube is connected with silicone rubber tubing to the pump via an 11.2L exposure chamber, a filter, and a flow meter. A target is placed in the exposure chamber at the start of the test and exposed to the corrosive atmosphere of the gas sample for 60 min or until the specimen has lost 70% of its total mass loss, whichever occurs first. 

This study revealed no significant corrosion of material used during 40 years in sodium coolant, so it was possible to continue operation of the BR-10 reactor circuits (this study and laboratory tests of structural materials at 500°C have shown that the circuit components made of similar stainless steels can be used in sodium for 60 years without worsening of their... 

Figure 7 Aspects of the nucleation of SCC by localized corrosion, (a) Peak aged Al-Li-Cu-Mg alloy 8090 after unstressed preexposure in aerated 3.5% NaCl for 7 days, (b) SCC initiated from one of the fissures shown in (a), following removal of the solution and continued exposure to laboratory air under a short transverse tensile stress (courtesy of J. G Craig, unpublished data), (c) Creviced region of 316L stainless steel after a slow strain rate test in 0.6M NaCl + 0.03M Na2S203 at 80°C and an applied anodic current of 25 xA, showing unstable pitting leading to crevice corrosion and SCC initiation (courtesy of M. I. Suleiman).

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