Corrosion specifications

As noted previously, dealloying also affects pre-boiler components manufactured of cast iron, such as FW pumps and valves. These components may, under certain (long-term) circumstances, suffer a selective form of preferential leaching galvanic corrosion. Specifically, graphitic corrosion may take place when the (anodic) iron matrix con-... 

Although there is no ASTM specification for gasoline mercaptan or hydrogen sulfide levels, a copper corrosion specification does exist. Since mercaptans and hydrogen sulfide attack copper and copper-containing alloys such as brass and bronze, it is important to minimize fuel mercaptans and hydrogen sulfide concentrations. 

Although no ASTM ferrous metal corrosion specification exists now for gasoline, diesel fuel, and other fuels, many refiners and marketers have adopted the National Association of Corrosion Engineers (NACE) Corrosion Standard Method TM-01-72-93 as a specification. This method has also been utilized by most product pipeline companies and is an established requirement. The NACE corrosion method is summarized as follows ... 

In the development of photoelectrochemical (PEC) solar cells, one of the most difficult problems is the corrosion problem. In any solvent, but particularly in solvents with water present, anodic currents flowing from the solid to the solution will usually lead to corrosion. Specifically the corrosion will take the form of anodic oxidation of the semiconductor, with the products remaining as a film, dissolving into the solution, or evolving as a gas. Any such action will degrade the solar cell. 

Design Metal Including Corrosion Specif ication Special... 

A convenient model for studying crevice corrosion specifics at the metal-plastic interface turned out to be the polymer coating on a metal substrate system. 

Other areas of corrosion concern are the membrane seals. If the seals are composed of flexible graphite, a preferred sealing material as discussed above, then corrosion by the common feed stream constituents is not a problem. However, with any metal seal - whether it be a brazed, welded, or soft-metal gasket seal - it is prudent to evaluate the potential for corrosion specifically at the seal. This evaluation is complicated by the fact that with brazed and welded seals, the metallurgy of the seal is influenced by the addition of the membrane alloy to the liquid braze alloy or weld pool. Experience has shown that welded seals to Pd—40Cu membranes, in which the membrane is welded to either Monel or 304L stainless steel, rapidly fail when subjected to 50 ppm hydrogen sulfide at 400 °C. 

Stmctural materials. All stainless steel constmction and material selection to minimize corrosion, specifically, to ensure 60 year vessel design life per module. ... 

Modem industrial facilities usually are equipped with systems that form the foimdation for the second requirement. Historical inspection data, failure analysis reports, analytical chemistry records, databases of operational parameters, and maintenance management systems are usually in place. The main task, therefore, is one of combining and integrating corrosion data into these existing (computerized) systems. In many organizations, much of the technical infrastructure required for achieving corrosion process control is already in place. Only the addition of certain corrosion-specific elements to existing systems may be needed. 

Another case is when microbial deposits produce components, such as inorganic and organic acids, that will change the local environment and thereby induce corrosion. Specifically, the production of inorganic acids leads to hydrogen ion production, which may contribute to hydrogen embrittlement of the colonized metal. 

Finally, other tests to control jet fuel corrosivity towards certain metals (copper and silver) are used in aviation. The corrosion test known as the copper strip (NF M 07-015) is conducted by immersion in a thermostatic bath at 100°C, under 7 bar pressure for two hours. The coloration should not exceed level 1 (light yellow) on a scale of reference. There is also the silver strip corrosion test (IP 227) required by British specifications (e.g., Rolls Royce) in conjunction with the use of special materials. The value obtained should be less than 1 after immersion at 50°C for four hours. 

At this point in time, the total sulfur content of crudes was not taken into consideration, since most of them were produced and refined in the United-States and contained less than 1%, and only the gasoline coming from corrosive crudes needed sweetening (elimination of thiols) for them to meet the specifications then in force. Today all crudes containing more than one per cent sulfur are said to be corrosive . 

When a customer agrees to purchase gas, product quality is specified in terms of the calorific value of the gas, measured by the Wobbe index (calorific value divided by density), the hydrocarbon dew point and the water dew point, and the fraction of other gases such as Nj, COj, HjS. The Wobbe index specification ensures that the gas the customer receives has a predictable calorific value and hence predictable burning characteristics. If the gas becomes lean, less energy is released, and if the gas becomes too rich there is a risk that the gas burners flame out . Water and hydrocarbon dew points (the pressure and temperature at which liquids start to drop out of the gas) are specified to ensure that over the range of temperature and pressure at which the gas is handled by the customer, no liquids will drop out (these could cause possible corrosion and/or hydrate formation). 

The end product specification of a process may be defined by a customer (e.g. gas quality), by transport requirements (e.g. pipeline corrosion protection), or by storage considerations (e.g. pour point). Product specifications normally do not change, and one may be expected to deliver within narrow tolerances, though specification can be subject to negotiation with the customer, for example In gas contracts. 

Produced water has to be separated from oil for two main reasons, firstly because the customer is buying oil not water, and secondly to minimise costs associated with evacuation (e.g., volume pumped, corrosion protection for pipelines). A water content of less than 0.5% is a typical specification for sales crude. 

The most common contaminants in produced gas are carbon dioxide (COj) and hydrogen sulphide (HjS). Both can combine with free water to cause corrosion and H2S is extremely toxic even in very small amounts (less than 0.01% volume can be fatal if inhaled). Because of the equipment required, extraction is performed onshore whenever possible, and providing gas is dehydrated, most pipeline corrosion problems can be avoided. However, if third party pipelines are used it may be necessary to perform some extraction on site prior to evacuation to meet pipeline owner specifications. Extraction of CO2 and H2S is normally performed by absorption in contact towers like those used for dehydration, though other solvents are used instead of glycol. 

The mechanical performance of equipment is likely to deteriorate with use due to wear, corrosion, erosion, vibration, contamination and fracture, which may lead to failure. Since this would threaten a typical production objective of meeting quality and quantity specifications, maintenance engineering provide a service which helps to safely achieve the production objective. 

The specific test was made into a specialized bunker of one partner of the CIAPES program. All the vessel was covered by AE sensors to locate witli accuracy AE sources. The corrosion defect was situated on the bottom of the vessel. The service pressure of the vessel was 8 bars, so the vessel was first submitted to a proof test at 12 bars. During this test, the pressure was increased with load holds in order to verify the assessment criteria. After the first hold at 4 bars, a cluster was located at the position of the defect. The number of events located in this cluster increased during all the test (figure 1). 

Corrosion suppression by inhibitors can be achieved by adding chemical species to tlie environment, which lead to a strong reduction of tlie dissolution rate. Depending on tlieir specific action, corrosion inliibitors can be divided into tlie following groups. 

C2.8.5 BRIEF OVERVIEW OF OTHER SPECIFIC CASES OF CORROSION... 

A process involving combined corrosion and straining of the metal due to residual or applied stresses. The occurrence of stress corrosion cracking is highly specific only particular metal/environment systems will crack. 

The most direct effect of defects on tire properties of a material usually derive from altered ionic conductivity and diffusion properties. So-called superionic conductors materials which have an ionic conductivity comparable to that of molten salts. This h conductivity is due to the presence of defects, which can be introduced thermally or the presence of impurities. Diffusion affects important processes such as corrosion z catalysis. The specific heat capacity is also affected near the melting temperature the h capacity of a defective material is higher than for the equivalent ideal crystal. This refle the fact that the creation of defects is enthalpically unfavourable but is more than comp sated for by the increase in entropy, so leading to an overall decrease in the free energy... 

Reactor-grade zirconium is essentially free of hafnium. Zircaloy(R) is an important alloy developed specifically for nuclear applications. Zirconium is exceptionally resistant to corrosion by many common acids and alkalis, by sea water, and by other agents. Alloyed with zinc, zirconium becomes magnetic at temperatures below 35oK. 

It is reported that mild carbon steels may be effectively protected by as little as 55 ppm of KTc04 in aerated distilled water at temperatures up to 250oC. This corrosion protection is limited to closed systems, since technetium is radioative and must be confined. 9sTc has a specific activity of 6.2 X lOs Bq/g. Activity of this level must not be allowed to spread. 99Tc is a contamination hazard and should be handled in a glove box. 

There is no specific antidote for acrolein exposure. Treatment of exposure should be directed at the control of symptoms and the clinical condition. Most of the harmful effects of acrolein result from its highly irritating and corrosive properties. 

As noted, the oxidation resistance of silicon nitride ceramics depends on the type and concentration of the sintering aids. In materials designed for high temperature appHcations the specific weight gain resulting from oxidation upon a 500-h air exposure at 1200°C and 1350°C is about 1—2 g/m and 2—4 g/m, respectively. The kinetics of the oxidation process have been iavestigated (63,64) as has the corrosion resistance (65). Corrosion resistance is also dependent on material formulation and density. 

Caustic soda is classified as a corrosive material by the DOT and DOT regulations and specifications must be followed for handling, labeling, and transportation in containers. Warning labels are recommended for containers of caustic soda solutions and anhydrous caustic soda by the MCA (79). The DOT identification number is UN1824 for 50 or 73% Hquid, and UN1823 for anhydrous caustic. 

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