Coatings

Internal lining testing methods against depressurisation: ISO 15741 vs NACE TM0184

Contents ISO 15741, Annex C NACE TM 0185 Coating type Liquid epoxy as internal coating Plastic coating Objects Steel pipes and fittings Tubular good Media Non-corrosive gas phase;  nitrogen Corrosive media ( H2S) and /or Chloride solution; hydrocarbon phase DFT 60~ 100 μm (4.3.3) Not specified temperature Not specified Elevated temperature required Pressurizing system Ramping 1 bar/min Continuous monitoring Depressurizing rate Release pressure rapidly ( no more than 5 min) Cool to 93oC,  and depressurized at a uniform rate to ATM within 15~ 30 mins Testing panel Type I : 100 mm x 50 mmx 1 mm Type II: 100…
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Metal Dusting: recent progress and industrial experience

The metal dusting is one of major failure mechanisms of equipment in producing process of hydrogen, ammonia, and syngas, as well as methanol reforming.  Although it has been recognized for the decades, there are still controversies in its mechanism.  With the recent development in metal dusting research, industries are having better understanding and may develop practical approaches to combat this type of failure. In this report, the recent research of metal dusting mechanism is summarized. It is reasonable to group these mechanisms in 3 types per Szakálos’ proposal: Type 1: decomposition of metastable carbides (e.g. cementite), Type 2: decomposition of…
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Corrosion under Polluted Atmospheric Environment

The atmospheric corrosion is probably the most common forms corrosion in daily life. The corrosion rate of steel is very much influenced by atmospheric environment. Under heavily polluted atmospheric environment, the corrosion is much severer than it in unpolluted environment. The factors of significance in atmospheric corrosion are time of wetness, rain, fog, dew are all contributing to the wetness. Temperature, particulate matters, wind direction, salt deposition and presence of pollutants etc are of great importance in atmospheric corrosion process. In an urban area and heavily industrial polluted zone, it has been proven both gaseous and solid forms of pollutants…
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DC STRAY CURRENT ANALYSIS AND MITIGATION

Introduction DC stray current is defined as current flowing through the path other than the intended. The DC stray current could be either natural sources, e.g. telluric, metallic mineral deposit, or artificial sources, e.g. foreign pipeline, HVDC transmission line, DC tram, etc. DC stray current is a big threat in pipeline integrity. The severity of the risk is a related to the soil resistivity: the lower the soil resistivity, the more likely to form such electrical conductance path, i.e. stray current related corrosion. The root cause of sewer explosion in 1992 Guadalajara Mexico is stray current corrosion of ductile iron pipe….
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