Inhibition, corrosion inhibitor efficiency

Acylated derivatives of amino acids are generally converted by microbes in rivers and lakes into acids and natural amino acids. Effectiveness data on mild and stainless steels proved the importance of the acyl moiety. The longer alkyl moiety in the acyl substituent (Cg io) greatly improves the corrosion inhibitor efficiency. These detergent-like compounds inhibit the deposition of both organic and inorganic particles, and... 

In another preliminary evaluation of the use of the 6-dimensional eigenvalues from the LDM as universal descriptors we looked at building a model of the inhibitive properties of heterocyclic diazoles for acidic iron corrosion [96]. Table 3.5 shows the computed eigenvalues and corrosion inhibitor efficiencies (CIE %) for a set of diazoles reported by Babic-Samardzija et al. [96]. 

To meet sales specifications, gas produced at the wellheads must be free of water and hydrocarbon liquids. Twin turboexpanders are a key component in this process, providing dewpoint control with optimal efficiency. Initial processing takes place at the wellhead platforms, where methanol is injected to inhibit hydrate formation. A corrosion inhibitor is also added to prevent gas from damaging downstream equipment. 

Dissolved solid and gaseous impurities can also affect the pH of the system and this may often lead to decreased inhibitor efficiency. In industrial plant, cooling waters can take up SOj, HjS or ammonia and pH control of inhibited waters will be necessary. The leakage of exhaust gases into engine coolants is an example in which corrosion can occur despite the presence of inhibitors. 

Reaction of adsorbed inhibitors In some cases, the adsorbed corrosion inhibitor may react, usually by electro-chemical reduction, to form a product which may also be inhibitive. Inhibition due to the added substance has been termed primary inhibition and that due to the reaction product secondary inhibition " . In such cases, the inhibitive efficiency may increase or decrease with time according to whether the secondary inhibition is more or less effective than the primary inhibition. Some examples of inhibitors which react to give secondary inhibition are the following. Sulphoxides can be reduced to sulphides, which are more efficient inhibitorsQuaternary phosphonium and arsonium compounds can be reduced to the corresponding phosphine or arsine compounds, with little change in inhibitive efficiency . Acetylene compounds can undergo reduction followed by polymerisation to form a multimolecular protective film . Thioureas can be reduced to produce HS ions, which may act as stimulators of... 

The Corrosion Inhibitor, Inhibiting Corrosive Efficiency and Its Relationship with Collector Action... 

To increase equipment reliability and plant efficiency, corrosion inhibitors are used in boiler and cooling water programs to control fouling and deposition on critical heat-transfer surfaces. In cooling systems, corrosion inhibition is commonly achieved through the use of passivators, which encourage the formation of a protective metal oxide film on the metal surface ( 1). ... 

A corrosion inhibitor is a chemical substance that, upon addition to a corrosive environment, results in reduction of corrosion rate to an acceptable level. Corrosion inhibitors are generally used in small concentrations. The principles and applications of corrosion inhibitors are discussed at great length in a recent monograph.47 A corrosion inhibitor should not only mitigate the corrosion, but also be compatible with the environment in the sense that it should not cause any complications. Usually the corrosion inhibitor is rated in terms of inhibition efficiency I and is given by the relationship. 

Attack by organisms other than SRB. Ammonia and amines are produced by microbial decomposition of organic matter under both aerobic and anaerobic conditions (ammo-nification). (Stott)5 These compounds are oxidized to nitrite by aerobic bacteria such as Nitrosomonas or Nitrobacter species. Nitrobacter is very efficient at destroying the corrosion-inhibition properties, of nitrate-based corrosion inhibitors by oxidation, unless a biocidal agent is included in the formulation. The release of ammonia at the surfaces of heat-exchanger tubes has a detrimental effect. (Stott)5... 

Anodic passivation of steel surfaces can be efficiently achieved by metal chromates. Chromates of Intermediate solubility (e.g., zinc chromate and strontium chromate) allow a compromise between mobility in the film and leaching from the film to be achieved. Chromates inhibit corrosion in aqueous systems by formation of a passivating oxide film. The effectiveness of chromate inhibitors in aqueous systems depends on the concentration of other ionic species in solution, for example, chloride. Synthetic resin composition can also significantly influence the effectiveness of chromate pigments. The effect appears to be related to the polarity of the resin (20) chromate pigments appear to be less effective in resins of low polarity. 

The efficiency of polymer materials as an anticorrosion mean of protection of metal parts from corrosion can be significantly raised by modification of polymer binders using corrosion inhibitors for metals. In this case it becomes possible to realize both the barrier and inhibition mechanisms for metal protection from corrosion in the anticorrosion element. Anticorrosion polymer elements as a source of electric field can hamper corrosion processes and corrosion-mechanical wear of metal parts by the electrochemical mechanism. Realization of the barrier, inhibition and electrochemical mechanisms of anticorrosion protection with the help of polymers not only allows a profound improvement in the anticorrosion protection of metal parts but comes close to the creation of smart anticorrosion plastics and anticorrosion systems. 

Corrosion inhibitors are compared by their inhibiting efficiency (IE), the percentage that corrosion is lowered, compared with corrosion rate in their absence. 

Green corrosion inhibitors including amino acids have been investigated as inhibitors for Co [54], Ni [55], iron and mild steel [56] in acidic environments in the past three decades. The objective was to develop effective corrosion inhibitors with zero envi-romnental impact. The inhibition effect of tryptamine (TA) was tested by Moretti et al. [57] for ARMCO iron protection in 0.5 M deaerated sulfuric acid. At a concentration of 10 mM, the inhibition efficiencies were between 90% and 99%. 

The velocity effects on CO2 corrosion have been studied in several projects dealing with multiphase flow. Mechanistic models based on electrochemistry, reaction kinetics, and mass transfer effects have been developed, e.g. by Nesic et al. [6.28]. A semi-empirical model was presented by de Waard et al. [6.29]. This model and the corresponding experimental results are valid for cases without carbonate scales. Inhibition can be accounted for by inserting an inhibitor efficiency factor. A model mainly based on the same data as the one developed by de Waard et al. is included in the standard NORSOK M-506 [6.30], The application of the NORSOK model is based on a computer program. Common to these models is that they are valid for cases with a bulk phase of water. For mist flow and dewing conditions the calculation basis is inferior, but such conditions give low corrosion rates. 

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