Anticorrosion inhibitor

For many decades, chromate compounds have been successfully used as anticorrosive inhibitors in the surface treatment of aluminium and others alloys. The use of chromates is however restricted worldwide, as they are considered highly toxic and carcinogenic [1], This has stimulated research aimed at the development of effective and environmentally acceptable alternatives to chromates. To obtain the beneficial properties of chromatation, two approaches can be utilised passive [2] and active [3,4] corrosion protection. Passive protection is normally provided by a barrier film that prevents contact between the corrosive species and the metal surface and therefore hinders a corrosion process. However, when a defect is formed in the barrier layer, the coating cannot stop corrosion in that place. The second approach is active corrosion protection, which employs inhibitive species that can decrease corrosion activity. An important point is that both strategies must be used together to protect the metallic substrate adequately. 

The anticorrosion properties of lanolin have been utilized over a considerable period, and the product has the status of a temporary corrosion inhibitor (186) (see Corrosion and corrosion control). There is probably potential for greater use of the poorer grades of lanolin for long-term storage and protection of machine parts. Other uses have been reviewed in detail (182). 

Miscellaneous Derivatives. Fimehc acid is used as an intermediate in some pharmaceuticals and in aroma chemicals ethylene brassylate is a synthetic musk (114). Salts of the diacids have shown utUity as surfactants and as corrosion inhibitors. The alkaline, ammonium, or organoamine salts of glutaric acid (115) or C-5—C-16 diacids (116) are useflil as noncorrosive components for antifreeze formulations, as are methylene azelaic acid and its alkah metal salt (117). Salts derived from C-21 diacids are used primarily as surfactants and find apphcation in detergents, fabric softeners, metal working fluids, and lubricants (118). The salts of the unsaturated C-20 diacid also exhibit anticorrosion properties, and the sodium salts of the branched C-20 diacids have the abUity to complex heavy metals from dilute aqueous solutions (88). 

The more common bacteria found in infected soluble oil systems can degrade the inhibitors, emulsifiers and mineral oil components. They cause a loss of anticorrosion properties, increase of acidity and deterioration of the emulsion. These bacteria thrive in well-aerated systems, and are termed aerobic. 

The preparation of a corrosion inhibitor in the solid form allows the development of a new technique of continuous intensive anticorrosive protection for gas and oil pipelines, as well as for acidizing operations of oil wells [746]. The controlled dissolution of the solid inhibitor creates a thin protective layer on the metallic surface that prevents or minimizes the undesirable corrosion reactions. 

Unfortunately some corrosion stimulants, like Cl, SO or NO,, strongly oppose inhibition by anticorrosive pigments and inhibitors ( ). Steel corrodes in saturated aqueous solutions of an anticorrosive pigment in presence of small amounts of these stimulants, e.g. 1% w/w NaCl is sufficient to make a saturated aqueous extract of zinc chronate corrosive (7). Therefore, irrespective of environmental requirements, the usefulness of active anticorrosive pigments and inhibitors as well has beoome questionable. 

The incentive to eliminate environmentally undesirable materials, such as chromates, has led to the consideration of organic inhibitor compounds as anticorrosion additives. 

Alkoxybenzotriazoles are effective corrosion inhibitors of copper and copper alloy <90EUP397455). The anticorrosion of benzotriazole on copper has been studied by surface-enhanced Raman spectroscopy, elUpsometry, and electrochemical techniques <86MI 401-01). 

Preliminary results showed that these types of compounds are possible inhibitors of the corrosion of iron in acids. This anticorrosion behavior is believed to arise from the fact that a dithiocarbamate-substituted cobalt cyclam can affect the hydrogen evolution reaction within the system. A... 

Chromium phosphate has a low solubility. It is therefore nearly always used in combination with other anticorrosive pigments. It is an extremely good long-term inhibitor, but is less effective during the initial phase of corrosion protection. 

Typically, cooling systems that are to be decommissioned or shut down for a period of time should be stored dry. If this is not possible or if there are dead-legs or other water traps, the cooling water should be deconcentrated and conditions adjusted so that the LSI of the water is approximately +0.5. A conventional, multifunctional chemical inhibitor with a strong anticorrosive action should be used, typically at 3 to 5x the normal dose. The objective is to prevent the onset of corrosion. 

A) Surface protective additives (i) antiwear (AW)/extreme-pressure (or temperature) improver (EP), (ii) anticorrosion and rust inhibitor, (iii) detergent and dispersant, and (iv) friction modifier. Examples of protective additives are listed in Table 2.4. 

Figure 22.5 shows the current map above the surface of the sol-gel film loaded with NIR-sensitive containers recorded after 24 h of immersion before and after irradiation with an IR-laser. The corrosion disappears immediately after irradiation of the local defect area. Thus, the healing of the corrosion defect is induced by remote IR opening of the inhibitor-loaded containers near the defects. Moreover, these films are characterized by high anticorrosion ability during aging. 

In Figure 2 the clouding points of different oils are shown in dependence of pressure at 50°C. For simplicity the oils of different producers and applications are termed by the capitals A-F. The main characteristics of the oils are presented in Table 1. In addition to the different composition of their hydrocarbon content the oils contain a variety of additives, e.g. aging inhibitors, anticorrosives, detergents, pourpoint depressants, foam inhibitors and others. 

The protection of metal surfaces by anticorrosion agents " - is also applied to heat exchangers, in the hydrogen fluoride cleaning of surfaces, with printing inks, with primers for coatings, etc. A typical derivative having corrosion inhibitor and surfactant properties is represented by 583, employed on steel surfaces. ... 

Inhibitor A general term for any compound which will inhibit (i.e. slow down or stop) a reaction, generally by preventing propagation of the chain reaction or by passivation of surfaces, etc. The term is often used to describe any additive which will prevent a particular tendency during working operations (e.g. antioxidants, anticorrosion agents). 

Chromium has long been prized for its beauty as a polished coating on metals (see photo) and for its anticorrosive properties in stainless steel and other alloys. In trace amounts, chromimum (HI) is an essential nutrient. Chromium (VI) in the form of sodium dichromate is widely used in aqueous solution as a corrosion inhibitor in large-scale industrial processes. See margin note on page 574 for more details on chromium. 

Owing to their anticorrosive properties TPs (e.g., 205) serve as rust inhibitors in lubricants for magnetic recording materials (95JAP(K)07/65352) or in chemical-mechanical polishing systems (02JAP(K) 134442). 

Inhibitor. [Zschimmer Schwarz] Fatty acid alkanolamide anticorrosion additive for metal cleaning and metal working lubricant in drilling and cutting oils. 

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