Corrosion decarburization

Step 3. Methane gas evolves during decarburization corrosion and builds up pressure, causing hydrogen embrittlement metal fatigue and eventual tube ... 

Various forms of high temperature corrosion including long-term overheating, decarburization, and hydrogen embrittlement... 

Overheating effects and high-temperature corrosion 240 decarburization 262... 

Hydrogen embrittlement is another important corrosion problem that is encountered in reformed-gas pipelines. The Nelson curves list the operating limits that should be followed to avoid decarburization and Assuring of steel in hydrogen service.88... 

A number of internal components, such as valves, valve seats, cylinder walls, pistons, and rings, will be exposed to hydrogen and water vapor. The potential effects are of two primary types (1) decarburization of steels and cast iron and (2) hydrogen embrittlement of aluminum pistons. Water vapor could cause excessive corrosion of exhaust systems, but this could be minimized by use of titanium. 

Hydrogen present in alkali metals is reactive. It may cause harmful corrosion reactions with several structural materials. Brittleness is caused by penetration with hydrogen, and decarburization caused by the formation of methane weakens the materials. Several other non-metals react with hydrogen dissolved in alkali metals. Such solutions may even be applied as process fluids for hydriding reactions. 

Therefore the helium atmosphere with the impurities must be adjusted in such a way that stable protecting oxide layers form on the surfaces (without Hj-production) in order to avoid an inner oxidation as well as a carburization or a decarburization, or other corrosion attacks. 

High-temperature corrosion is considered to be electrochemical in nature, with the high-temperature scale formed acting as an electrolyte. Corrosion is usually uniform in nature. The predominant effects are oxidation and carburization/decarburization. Changes in mechanical properties, specifically a loss of ductility due to phase changes, also take place. 

Among the nonmetalhc elements, oxygen and carbon have a prominent role for what concerns corrosion and mechanical resistance of stmctural materials in liquid sodium. This is because of, as already mentioned, Na and oAict metaUic alloying elements, such as Fe and Cr, can form ternary oxides. On the other hand, for what concerns the impact of carbon, carburization/decarburization processes of the structural materials can occur with consequences on the mechanical properties of the material. 

The selective leaching or corrosion of a specific constituent (Al, Ni, Mo, Ni) from an alloy. Decarburization... 

Corrosion from impurities (including fission products), carburization/decarburization,... 

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