Corrosion ionic product

Sweeping away corrosive ionic species. The attack of stainless steel decreases as the solution flow speed increases. Stainless steel in nitric acid without agitation, is attacked autocatalytically because of the formation of nitrous acid, as a cathodic reaction product. 

The final type of boundary layer results from chemical reactions of metal surfaces with the slurry chemicals. During metal CMP, the slurry chemicals react with the metal surface and form either solid or ionic products or both. Such reactions are considered corrosion reactions. Formation of solid species occurs on the metal surface, forming a surface layer which, to varying de-... 

Some ionic liquids have been found to release highly toxic and very corrosive degradation products when undergoing hydrolytic decomposition. This discovery was especially harmfiil for the green image of ionic liquids as it addressed, in particular, the main work horses of ionic liquid research of the time, namely the hexafluorophosphate and tetrafluoroborate systems which indeed release HF on contact with water [47]. Today, we know that many ionic liquids are very stable to hydrolysis. Moreover, we have developed many ionic liquids which are completely halide-free [48] so that the release of HQ or HF can certainly be avoided in both hydrolysis and combustion processes. 

An important feature of a corrosion process is the reduction of the dissolved oxygen by formation of hydroxyl ions (OH"). Since the equilibrium potential is linked through the concentration of the OH" ions with the concentration of the hydrogen ions with the (or H3O+ ions) by the ionic product of water (6 +)(fl jj ) = = 10 " at 25°C, the equilibrium potential is pH-dependent. The standard... 

This data indicates that water becomes increasingly dissociated and hence acidic as the temperature rises (Figure 18.7). The increase in the ionic product of water, K , with temperature accounts for the corrosive action of hot pure water on iron pipes this behaviour is caused by the increase in concentration of hydrogen ions. The pH decreases with an increase in temperature but the solution is still described as chemically neutral since the concentrations of hydroxide and hydrogen ions remain equal. 

The environment plays several roles in corrosion. It acts to complete the electrical circuit, ie, suppHes the ionic conduction path provide reactants for the cathodic process remove soluble reaction products from the metal surface and/or destabili2e or break down protective reaction products such as oxide films that are formed on the metal. Some important environmental factors include the oxygen concentration the pH of the electrolyte the temperature and the concentration of anions. 

Sodium hydroxide, NaOH, is a soft, waxy, white, corrosive solid that is sold commercially as lye. It is an important industrial chemical because it is an inexpensive starting material for the production of other sodium salts. The amount of electricity used to electrolyze brine to produce NaOH in the chloralkali process (Section 12.13) is second only to the amount used to extract aluminum from its ores. The process produces chlorine and hydrogen gases as well as aqueous socFinn hydroxide (Fig. 14.17). The net ionic equation for the reaction is... 

One of the key challenges for this process is dealing with the wide range of contaminants in the waste HBr stream. Both inorganic and organic contaminants may be present. These contaminants are typically reactants and products of the upstream bromination process which generated the waste HBr. In addition, they may include corrosion products of upstream equipment or ionic materials present in the water used to scrub the gaseous bromination process effluent. The main concerns about contaminants in the feed streams are their effect on catalyst activity and stability and their effect on bromine product quality. 

In the Eastman process for 2,5-dihydrofuran production, the situation is different and the problem of heavy products has been tackled in a highly original manner. [31] The oligomers formed in the process are highly polar and insoluble in alkanes. The ionic liquid, [P(oct)3C18H37]I and the Lewis acid catalyst, [Sn(oct)3]I, which are non toxic (LD50 > 2 g kg"1 for each), non-flammable (flammability 1) and non-corrosive (340 stainless steel is used for the reactor), have been designed to be soluble in... 

Halogen content If halogens in the anion are not crucial for specific reactions performed in the ionic liquid, they should be avoided. Moisture sensitivity, halogenide transfers, alcoholysis and toxic effects are often connected with halogen atoms in the molecule [27]. In addition, the hydrolysis products HCl or HF act corrosively. Within the project reported by Wasserscheid and coworkers they successfully developed ionic liquids with alkylsulfate groups as anions to overcome the halogen content. These new solvents show very favorable properties. 

An area of broad interest in catalysis is the search for viable replacements for the widely used Bronsted liquid acids such as HF and H2SO4 and solid Lewis acids such as AICI3 and MgCl2. The liquid acids are corrosive and also costly, because of the need to work up the products by neutralization and repeated washing. In many cases, the contamination of the products by these acids induces degradation over time and limits the application of the products. The cost of multi-step washing can be quite high. Acidic ionic liquids therefore offer potential alternatives for such reactions (//). 

The primary advantage in the first step of the method described here (using 1-chlorobutane diluted in MeCN) is that it eliminates long reaction periods and allows the use of secondary alkyl halides without competitive elimination reactions. For example, the reaction of sec-butyl bromide with N-methylimidazole using the classical method (in neat alkyl halide) produces, along with the desired product, 20-30% of butenes and 1-methylimidazole hydrobromide. In the second step, the use of water as solvent allows the anion metathesis reaction to be quantitative in a very short time and allows the easy purification of the ionic liquids. Moreover, employing the potassium salt avoids the use of corrosive and difficult to handle hexafluorophosphoric add and the expensive silver tetrafluoroborate. ... 

For hydrogen production from water, pure water (pH=7.0) is seldom used as an electrolyte. Water is a poor ionic conductor and hence it presents a high Ohmic overpotential. For the water splitting reaction to proceed at a realistically acceptable cell voltage the conductivity of the water is necessarily increased by the addition of acids or alkalis. Aqueous acidic and alkaline media offer high ionic (hydrogen and hydroxyl) concentrations and mobilities and therefore possess low electrical resistance. Basic electrolytes are generally preferred since corrosion problems are severe with acidic electrolytes. Based on the type of electrolytes used electrolyzers are... 

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