Hydrogen blistering

Hydrogen blistering is the result of cyanide-induced corrosion in the light ends section of the unit, usually the top of the absorber. The simplified chemical reactions are as follows  

Normally, a layer of FeS scale, produced in the first reaction, protects the interior of the pipe or vessel. However, in the second reaction, cyanide removes the FeS protective scale exposing more free iron to react with H2S and releasing more hydrogen. Without protection, this cycle continues until blistering, cracking, and eventual total corrosion of equipment occurs. 

Install a water-wash system for dilution and removal of cyanide from the unit. Cascading wash water from the high-pressure zone back to the main column overhead or to the first-stage wet gas compressor outlet is attractive, but it is better to use overhead water and pump it from low pressure to high pressure. 

Add polysulfide solution to neutralize the cyanide. Air can be injected into the main column overhead to make polysulfide. 

Inject a Dehazer Additive into the High Pressure Separator (HPS) 

Specimens were subjected to cathodic hydrogen charging for six months in a solution 0.004 wt% of H2SO4 in distilled water at pH 3.2 with a current density of 0.1 mA/cm. In Fig. 14.35a and b it is possible to see the blisters appeared at the surface, while in (c) and (d) the same blisters appear in a cross section of the specimens. At higher temperatmes, usually over 200 °C, in carbon steels the presence of iron carbide (cementite) can also favor the methane formation through the reaction 

Also in this case, the methane gas pressure continuously grows till final fracture. Moreover, the carbon impoverishment, because of the methane gas formation, weakens the metal. 

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Hydrogenations Hydrogen blistering Hydrogen bomb Hydrogen bonding... 

Skei and Wachttr, Hydrogen Blistering of Steel in Hydrogen Sulfide Solutions," Corrosion, May 1953. 

Decarburization results from hydrogen absorption from gas streams at elevated temperatures. In addition to hydrogen blistering, hydrogen can remove carbon from alloys. The particular mechanism depends to a large extent on the properties of other gases present. Removal of carbon causes the metal to lose strength and fail. 

To prevent or minimize hydrogen blistering and embrittlement, the following methods should be considered ... 

Ultrasonic techniques. Wall thickness can be measured to monitor the progress of general corrosion, cracks can be detected and hydrogen blisters identified. Certain construction materials such as cast iron cannot be examined by ultrasound. Skilled operators and specialist equipment is required. Plant can be examined in situ except when it is above 80°C. 

Most refiners employ continuous water wash as the principal mei of controlling corrosion and hydrogen blistering. The best sourc water is either steam condensate or well-stripped water from a water stripper. A number of refiners use ammonium polysulfat neutralize hydrogen cyanide and to control hydrogen stress crack... 

At lower pH values, hydrogen ions are discharged, whereas at higher pH values, the magnetite layer thickens coarsely, becomes porous, and may peptize. Hydrogen blistering also may occur. 

Fe, etc. carbon steel none predicted iron/chlorine fire if above 250°C (or 100°C with impurities) hydrogen blistering between steel laminations none predicted material of construction ... 

Hydrogen blistering blistering of steel caused by trapped molecular hydrogen formed as atomic hydrogen during corrosion of steel by hydrogen sulfide. 

Figure 6.62 Cross-section of carbon steel plate showing a large hydrogen blister removed after 2 yr exposure from a petroleum process stream16...

Hydrogen blistering blister formation, originating at nonmetallic inclusions. 

One can prevent the formation of hydrogen blisters by using a clean steel without voids such as killed steels instead of rimmed ones. Manufacturing processes and... 

Figure 7.82 Hydrogen blister in NPS 6 sour gas pipeline (Courtesy of Malcolm Hay)...

F. Paredes and W. W. Mize. Unusual Pipeline Failures Traced to Hydrogen Blisters. Oil and Gas Journal 52(12) 99 (1954). 

Hydrogen attack at ambient temperatures a. Hydrogen Blistering... 

Hochbauer, T., Nastasi, M., Mayer, J.W. Hydrogen blister depth in boron and hydrogen coimplanted n-type silicon. Appl. Phys. Lett. 75, 3938 (1999)... 

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