Hydrogen cracking

Often contain defects (hydrogen cracks, slag inclusions, stop-start marks). Help initiate fatigue cracks. Critical welds must be tested non-destructively and defects must be gouged out. 

Erosion —corrosion, fretting corrosion, impingement attack, cavitation damage stress corrosion cracking, hydrogen cracking, corrosion fatigue... 

The importance of occluded cells cannot be overemphasised, and Brown considers that pitting, crevice corrosion, intergranular attack, filiform corrosion and hydrogen cracking are characterised by local acidification due to hydrolysis of metal ions, and that this phenomenon is of major significance in the overall mechanism. 

In recent years some additional data on the corrosion resistance of the Ni-Fe alloys has been generated, but it is fairly limited and the foregoing material summarises the majority of the available information. The additional data falls into the categories, electrochemical, resistance to acids and resistance to hydrogen cracking. 

Gas-phase deposition In this process, a halide of the solute metal is passed in vapour form over the surface of the metal to be coated, which is heated to a temperature at which diffusion can take place. Temperatures of 500-1 300°C or more can be used, depending on the particular system considered. Generally, filler atmospheres are provided to carry the halide vapour these atmospheres are usually reducing gases such as hydrogen, cracked ammonia, etc. or inert gases (helium, argon). 

Finally, it is necessary to point out that although a particular method of corrosion control may be quite effective for the structure under consideration it can introduce unforeseen corrosion hazards elsewhere. Perhaps the best example is provided by cathodic protection in which stray currents (interaction) result in the corrosion of an adjacent unprotected structure or of steel-reinforcement bars embedded in concrete a further hazard is when the cathodically protected steel is fastened with high-strength steel bolts, since cathodic protection of the tatter could result in hydrogen absorption and hydrogen cracking. 

Issues related to HE of steel liner may still exist however, due to the thin steel liner carrying lower stresses, potential for hydrogen cracking could be reduced. 

MHC [Mitsubishi hydrocracking] A process for making benzene and other aromatic hydrocarbons by hydrogenating cracked petroleum fractions. 

P. A. Klein and R. A. Hays, The Hydrogen Cracking Initiation Susceptibility of HY-I30 Steel Base Plates and Weldments in Marine Enviroments, (1989), David Taylor Research Center, Annapolis, MD. 

Hydrogenation Gasoline to heavy feedstocks Low-boiling products 400-850°F 205-455°C Mild hydrogenation cracking removal of sulfur, nitrogen, oxygen, and metallic compounds... 

E. M. Moore, J. J. Warga. Factors Influencing the Hydrogen Cracking Sensitivity of Pipeline Steels. NACE Corrosion/76 Paper 144, Houston, Texas, U.S.A., 1976-03-22/26, and Materials Performance 15(6), 17 (1976). 

A refinement to the CE is the parameter Pern, which has been developed to predict hydrogen cracking susceptibility as it relates to weldability. The Pcm chemistry parameter, applicable to most low-alloy steels having less than -0.18% carbon, is defined as ... 

---