Hydrogen cracking inhibitor

Where HjS is present, line failures due to penetration underneath pits can occur in a short time. The sulfide film formed may be anodic to the metal surface, and afford some degree of corrosion protection. In many cases, however, the layer of FeS is not continuous and if so, may be porous. The net result is pit formation and growth. Sulfide stress cracking and hydrogen embrittlement are also factors to consider in inhibition for HjS. In systems where H2S and CO2 are both present, the ratio of COj to HjS determines whether COj or H2S corrosion mechanisms will dominate. Inhibitors should be effective against both H2S and COj. 

The hexanes undergo side reactions even more readily than do the pentanes. Although disproportionation and cracking can be suppressed to some extent by the addition of cyclic hydrocarbons, this treatment is not effective enough to ensure satisfactory catalyst life, and hydrogen at relatively high pressure must be used as the inhibitor. 

These catalysts are sflica-aluminas whose cradcing and dispropordonatioq power has been altered by steam treatment, the use of an inhibitor, or of alui as containing a halogenated compound or fluorine. They are very rugged, are empfoyed without hydrogen and hence cannot isomerize ethylbenzene, which is therefore cracked or transformed by a disproportionation reacdon into benzene and Cio aromatics. Consequently, they can only be used with feeds poor in ethylbenzene. However, no naphthenic hydrocarbons are formed. 

A materials test equipment has been developed in Japan within the WE-NET project to investigate the environmental hydrogen embrittlement of specimens in high-pressure hydrogen up to 10 MPa at different temperature levels between 20 K and 1500 K. Additions of various gaseous inhibitors have been examined as a preventive technique to arrest crack growth in the materials [129]. 

Recommendations for Selecting Inhibitors for Use as Sucker Rod Thread Lubricants Sulfide Stress Cracking Resistant Metallic Materials for Oil Field Equipment Metallic Materials for Sucker Rod Pumps for Hydrogen Sulfide Environments Control of Internal Corrosion in Steel Pipelines and Piping Systems... 

Water also inhibits the stress corrosion cracking of steel in ammonia, and titanium in methanol, as well as attack on titanium by dry chlorine. A trace of water (0.001%) in liquid hydrogen fluoride (HP) behaves as a passivating inhibitor for nickel. This is an extreme example of the importance of solvent-inhibitor interactions. The exact mechanism of inhibition by water in HF is unknown, but the passivating effect is similar to that observed on steel in the presence of chromates in aqueous solution. 

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