Hydrogen damage

Specific types of hydrogen damage, some of which occur only in specific alloys under specific conditions include  

Hydrogen embrittlement Occurs most often in high-strength steels, primarily quenched-and-tempered and precipitation-hardened steels, with tensile strengths greater than about 1034 MPa (150 ksi). Hydrogen sulfide is the chief embrittling environment. 

Hydrogen-induced blistering Also commonly referred to as hydrogen-induced cracking (HIC), it occurs in lower-strength (unhardened) steels, typically with tensile strengths less than about 550 MPa (80 ksi). Line pipe steels used in sour gas environments are susceptible to HIC. 

The body-centered crystal structures of carbon and low-alloy steels are susceptible to four types of hydrogen damage, two of which are low-temperature processes and two are high-temperature processes  

The diffusion of hydrogen through steels to harm mechanical properties involves atomic or nascent hydrogen because molecular hydrogen cannot 

Fundamentals of Metallic Corrosion Atmospheric and Media Corrosion of Metals 

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Figure 4-437. The simplified mechanism of hydrogen damage. (From Ref. [191].)...

Concern about hydrogen damage has lead to much debate regarding limits for protection potentials of high-alloy steels. However, it is thought that under normal seawater service and cathodic protection conditions, these materials will not be adversely affected provided that the microstructure has at least 40% austenite present . This latter point is of particular importance to welds and their heat affected zone where careful control of heat input is necessary to maintain a favourable microstructure. 

In high-pressure boilers, there are three types of on-load corrosion acidic chloride, neutral chloride/dissolved oxygen, and caustic attack. The first and second (once it becomes established) are brittle and thick-walled and are accompanied by hydrogen damage which can lead to failure within a few hundred hours. Caustic attack tends to produce a gouged appearance of the metal due to extensive wastage. The morphology is fairly characteristic of the failure type. Acidic chloride forms hard, laminated oxide, whilst, with caustic attack, the oxide is often soft, and, as it is easily removed, may be absent. 

Ultrasonics has been utilised in several versions of pipeline inspection vehicle see section below). The use of ultrasonics for detection of hydrogen damage in steels has been reported"". ... 

Hydrogen embrittlement (hydrogen damage) Only in boilers over 1000 psig, leading to violent tube rupture. 

High levels of hydrogen in steam do not necessarily indicate that hydrogen damage will occur. 

Hydrogen cation ion-exchange softening, with ED 374 Hydrogen damage 256... 

While both hydrogen partial pressure and temperature are important, particular attention should be given to obtaining the best estimate of accurate metal temperature. One method of obtaining more accurate data for a specific area is to attach a skin thermocouple to the area that previously exhibited high temperature hydrogen damage. 

The intrusive hydrogen probe (IHP-200) shown in Fig. 29 can be placed in access fittings in industrial plants (pressure vessels, pipelines) and withstands pressures up to 200 bar. It is typically used to monitor the efficiency of measures taken to diminish the risks of hydrogen damage (use of inhibitors, H2S scavengers, etc.). 

It is anticipated that refinement of the sensor design will provide the welding industry with a powerful tool for control of hydrogen damage in welded structures, especially those structures manufactured from high strength alloys where such control is most critical. 

Corrosion General corrosion, crevice corrosion, pitting, hydrogen damage, caustic corrosion, intergranular corrosion, microbiological corrosion... 

Underdeposit corrosion - caustic gouging Underdeposit corrosion - hydrogen damage Underdeposit corrosion - phosphate corrosion Acid cleaning corrosion Internal deposit/corrosion product buildup Fireside wastage Fireside oxidation... 

Caustic gouging Hydrogen damage Phosphate corrosion... 

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