Aqueous solutions corrosion prevention with

Atmospheric corrosion can be prevented by using volatile inhibitors which need not be applied directly to the surfaces to be protected. Most such inhibitors are amine nitrites, benzoates, chromates, etc. They are mainly used with ferrous metals. There is still some disagreement as to the mechanism of action. Clearly, any moisture that condenses must be converted to an inhibitive solution. There is no doubt that the widely used volatile inhibitors are effective in aqueous solutions containing moderate... 

Environments are either gases or liquids, and inhibition of the former is discussed in Section 17.1. In some situations it would appear that corrosion is due to the presence of a solid phase, e.g. when a metal is in contact with concrete, coal slurries, etc. but in fact the corrosive agent is the liquid phase that is always present. Inhibition of liquid systems is largely concerned with water and aqueous solutions, but this is not always so since inhibitors may be added to other liquids to prevent or reduce their corrosive effects — although even in these situations corrosion is often due to the presence of small quantities of an aggressive aqueous phase, e.g. in lubricating oils and hydraulic fluids (see Section 2.11). 

The corrosion of metal surfaces and the precipitation of a metal sulfide by an aqueous acid solution can be prevented by an aldol-amine adduct. Aldol (from acetaldehyde) CH3CH(OH)CH2CHO has been utilized as a H2S scavenger that prevents the precipitation of metal sulfides from aqueous acid solutions. However, when the aldol or an aqueous solution of the aldol is stored, the solution separates quickly into two layers, with all of the aldol concentrated in the bottom layer. The bottom layer is not redispersible in the top layer or in water or acid. In addition, the aldol in the bottom layer has very little activity as a sulfide scavenger. Thus the use of aldol as a H2S scavenger in aqueous acid solutions can result in unsatisfactory results [245,247]. However, the aldol can be reacted with an amine, such as monoethanoleamine (=aminoethanol), to form an aldol-amine adduct to overcome these difficulties. The amine utilized to prepare the aldol-amine adduct must be a primary amine. The aldol-amine adduct preferentially reacts with sulfide ions when they are dissolved in the... 

An interesting case arises when iron is immersed in alkaline solutions containing inorganic salts. For example, iron will remain bright in a 1 per cent, solution of caustic potash for an indefinite time, but upon addition of potassium chloride corrosion readily takes place. It is possible, however, to increase the alkali to such an extent that corrosion is entirely prevented, no matter how concentrated the solution of chloride. The minimum amount of alkali required rises with the percentage of chloride until saturation of the latter is arrived at. This is indicated in fig. 4. AK represents the solubility curve of potassium chloride in aqueous solutions of potassium hydroxide, and CE the maximum concentration of the chloride that may be present in the... 

Radiolysis has been used successfully in order to synthesize various noble (such as silver, gold and platinum) and non-noble (such as nickel and iron) metal nanoparticles in aqueous solution and also in other solvents such as alcohols. Due to their relatively low redox potential compared to that of the bulk, metal clusters can be oxygen-sensitive. However, the deoxygenation (by bubbling with an inert gas such as argon or nitrogen) of the solutions prior to irradiation and their study under inert atmosphere prevent their oxidation. Moreover, since water radiolysis leads to the formation of protons in addition to that of hydrated electrons, radio-induced acidification of the medium may lead to non-noble metal clusters corrosion. Therefore, to avoid the oxidation by protons, the solutions can be prepared in slightly basic medium. 

For tests conducted at high temperature, there are several concerns regarding safety that should be taken into accoimt. The first is that HT corrosion tests may involve test conditions that are above the atmospheric boiling point of the aqueous solution or even above the flash point of various combustible constituents in the test environment. Therefore, all precautions to prevent leakage from the test vessel should be taken prior to the initiation of testing. This usually includes a pressure test of aU fittings and seals with an inert gas prior to introduction of the corrosive environment. 

Even if the parts are made from stainless steel and other inert materials, the pumps should never be left overnight or for longer time with strongly acidic or basic mobile phases or with salt solutions. Columns with aqueous mobile phases should be washed first with an aqueous solution to remove salts and then with 70-100% methanol or acetonitrile for preventing corrosion, salt precipitation, and growth of microbes. 

The methacrylamide-MA copolymer has also been studied for purification of industrial waste water/ The disodium salt of MA has been copolymerized with the sodium salt of 2-acrylamido-2-methyl-propanesulfonic acid, using peroxide initiators, to give useful dispersant and deflocculants for water-insoluble compounds of Fe, Ca, Al, and for silt and clay particles/" The copolymers also prevent boiler scale formation, corrosion, etc., without being affected by the hardness of the water. Copolymers prepared in aqueous solutions are claimed to be useful in well wall materials, coatings for microcapsule production, and for paper dry-strength agents. 

The results of field tests on 250 units over an 18-month period have been summarized by Fbwler (1964). Calcium chloride has also been proposed for hydrate prevention in natural-gas gathering lines. In this application an aqueous solution is injected near the well head and collected at the downstream point after gas cooling has occurred. In tests reported in Russian literature (Andiyudichenko and Vasilchenko, 1963), the process was found to be very effective. However, purging of the solutions with natural gas prior to injection was found necessary to reduce their corrosive action. 

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