Corrosion Due to Hydrogen
Metals can be broken down by hydrogen corrosion, which results from many different sources, including dissociation of moisture, thermal decomposition of gases, and cathodic reactions. Hydrogen corrosion can lead to embrittlement, cracking, and reduction of a metal's load-bearing capacity.
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Dissociation and Embrittlement
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Hydrogen corrosion can be caused by the dissociation of moisture that results from casting and welding. Dissociation means that ionic compounds separate or split into smaller particles of matter; this process is known to weaken metals. Embrittlement causes a metal to fracture and it occurs when hydrogen is absorbed into an alloy. Welding or some other aspect related to the refining process usually leads to embrittlement.
Inclusions
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Metals like low-carbon steels can lose hydrogen atoms from their structure, and the loss of this element causes inclusions. Blisters will develop in the metal from hydrogen loss that occurs at inclusions within the metal. Hydrogen damage can ultimately lead to delamination (separation in layers) within a metal. When hydrogen atoms mix with a metal's atomic structure, hydrogen gas builds up within the substance. This build-up of hydrogen gas will cause a metal's atomic structure to weaken, and peeling occurs on the surface of the alloy as a result.
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Failure and other effects
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Hydrogen places strain on the load-bearing cross-sections of metals. Metals with low sulfur levels or that have been treated with hydrogen inhibiting additions (such as ferrosilicates) can help to reduce or eliminate the effects of hydrogen corrosion. Other problems such as sulphide stress corrosion cracking can occur in certain alloys, such as steel, from the effects of hydrogen.
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