Corrosion aqueous acids

In the context of coal cleaning, oxygen is often considered unimportant because it is nonpolluting. But some consideration should be given to the effect of oxygen on the fate of its nitrogen and sulfur compatriots as well as its effect when water (a product of the combustion of hydrocarbons which also contain oxygen) condenses with other by-products on the cooler parts of combustion systems corrosive, aqueous acids can be the result. 

Germanium tetrafluoride produces hydrogen fluoride in aqueous acidic solutions. Hydrogen fluoride is toxic and very corrosive. The OSHA permissible exposure limit (17) and the American Conference of Governmental Industrial Hygienists (ACGIH) TLV for fluoride is 2.5 mg/m of air (18). 

Table 3. 100-Day Metal Corrosion Rates in Aqueous Acid, mm...

Corrosion. Aqueous solutions of citric acid are mildly corrosive toward carbon steels. At elevated temperatures, 304 stainless steel is corroded by citric acid, but 316 stainless steel is resistant to corrosion. Many aluminum, copper, and nickel alloys are mildly corroded by citric acid. In general, glass and plastics such as fiber glass reinforced polyester, polyethylene, polypropylene, poly(vinyl chloride), and cross-linked poly(vinyl chloride) are not corroded by citric acid. 

Fission Product Extraction. Tables IV and V list the distribution ratios for most of the fission products produced in spent fuel. Also included are corrosion products Cr, Fe, and Ni. Extractant concentrations for DHDECMP, HHDECMP, and 0c >D[IB]CMP0 were selected on the basis of data in Figure 2. The aqueous acidity... 

Still bottom residues produced in the distillation of quinoline from coal tar can be oxidized and are suitable as a metal corrosion inhibitor for use in aqueous acid solutions [244]. 

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... 

The first illustration is fashioned after Problem 29 [13] of iron corrosion in deoxygenated aqueous acid. It is assumed that four identically shaped iron-containing specimens labeled A, B, C, D are chosen randomly, and inserted in the acid carrying a corrosion inhibitor. The percentage reduction in the specific rate loss is 93.3(A), 97.3(B), 96.7(C) and 90.0(D). As shown in Table 1, the hypothesis H of no treatment effect (i.e. the hypothesis of all rankings being equally possible) can be stated as... 

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... 

Corrosion of metals by aqueous acids with hydrogen evolution is usually rapid and fairly uniform across the surface (general corrosion), since the reductive dissolution of the oxide film that helps maintain the distinction between anodic and cathodic sites is favored by low pH (reaction 16.9). Thus, although local anodic and cathodic areas persist, pitting becomes less important than overall loss of metal. If the oxide film is sufficiently insoluble in acids and is also resistant to reductive dissolution, as with titanium or stainless (>11% Cr) steels, the metal may remain unaffected by aqueous acids, except at quite negative Eh values. In cases where the cathodic discharge of hydrogen ions... 

Figures 16.8 and 16.9 show only the anodic polarization curves for corrosion cells. The important question is, where do these curves intersect with the polarization curves for likely cathodic reactions, such as hydrogen evolution or oxygen absorption The intersection point defines the corrosion current density icorr and hence the corrosion rate per unit surface area. As an example, let us consider the corrosion of titanium (which passivates at negative Eh) by aqueous acid. In Fig. 16.10, the polarization curves for H2 evolution on Ti and for the Ti/Ti3+ couple intersect in the active region of the Ti anode. To make the intersection occur in the passive region (as in Fig. 16.11), we must either move the H+/H2 polarization curve bodily...

Figure 16.10 Active corrosion of titanium by aqueous acid.

An important drawback of the original Wacker process is the highly corrosive nature of the aqueous acidic PdCl2—CuCl2 system. Attempts were made to apply electrochemical reoxidation of palladium,513,514 and to use other oxidants,495 such as Fe(III) salts, Mn02, quinones,514-516 peroxides,517,518 and more recently, heteropoly acids.516,519"522... 

Dansyl chloride is a corrosive organic acid halide, which should be used only in a hood. Wear disposable gloves while using the reagent. If it is spilled on the skin, sprinkle with sodium bicarbonate and wash with copious amounts of warm soapy water. Rinse well. For floor or bench spills, cover with sodium bicarbonate and transfer mixture to a beaker of water. Pour the aqueous solution down the drain with excess water. Do not pipet solutions of dansyl chloride hy mouth ... 

The equipment can usually be constructed of carbon steel except for the hydrolysis vessel, which is usually glass-lined to avoid corrosion by aqueous acids. All vessels must be supplied with an inert gas (nitrogen or argon) for purging and blanketing and are vented to release off-gases. It is imperative that the reaction vessel be protected with a rupture disk. 

In most cases, the separation of alcohols, usually methanol, ethanol, and glycerol, is carried out contemporaneously with the separation of sugars and organic acids, and almost always the desire is to quantify all these analytes. It is seen, therefore, that the mobile phase is often an aqueous acid solution, even though only water may be used (5,9). Sulphuric acid is the one most frequently used, although phosphoric acid is preferred by some, since it is less corrosive on the components of the HPLC system (10). The concentration of sulphuric acid normally varies between 0.004 N and 0.01 N or more. The choice of acid may, however, be dictated by other considerations. This is the case, for example, with the use of a conductivity detector, which requires an appropriate conductivity suppressor system. If such a device is not available for a particular... 

The complex load at temperatures up to 600 °C, pressures higher than 21 MPa and fluid densities from 100 to 1000 kg/m on the one hand, and a - in some cases - highly corrosive aqueous environment on the other hand, can lead to fast corrosion of the construction materials of SCWO reactors. Chloride is the most important corrosive species in SCWO treatment of wastes. After the oxidation of neutral or acidic feeds, the pH of SCWO solutions is frequently rather low. To keep the chemistry as simple as possible hydrochloric acid has been used to simulate chlorine-containing wastes in SCWO environments. 

The dark side of hydrofluoric acid is its toxicity and corrosiveness. Aqueous and anhydrous HF readily penetrate the skin, and, because of its locally anesthetizing effect, even in very small quantities can cause deep lesions and necroses [4, 5]. An additional health hazard is the systemic toxicity of fluoride ions, which interfere strongly with calcium metabolism. Resorption of HF by skin contact (from a contact area exceeding 160 cm ), inhalation, or ingestion leads to hypocalcemia with very serious consequences, for example cardiac arrhythmia. 

Sulphuric acid (70%) [CORROSIVE] Aqueous formaldehyde (37%) [TOXIC] Ethanol [FLAMMABLE]... 

Concentrated sulphuric acid [CORROSIVE] Aqueous sodium chloride Distilled water... 

The aqueous corrosion of ceramics may involve a charge-transfer or electrochemical dissolution process. However, in many cases, dissolution or corrosion may take place with no charge transfer yet may be determined by one or more electrochemical factors such as absorbed surface charge or electronic band bending at the surface of narrow-band-gap semiconducting ceramics. The aqueous corrosion of ceramics is important in a number of areas. One of the most important is the stability of passive oxide films on metals. The stability of ceramics is a critical aspect in some aqueous photoelectrochemical applications (12), an example being the photoelectrolytic decomposition of water. Structural, nonoxide ceramics such as SiC or Si3N4 are unstable in both aqueous acid and alkaline environments the latter is virtually unstudied, however. 

Corrosion of automobile exhaust systems by direct reaction of the metal with high-temperature gases and by condensation of water and absorption of the oxides of sulfur and nitrogen to produce aqueous acid environments... 

Treatment with acids It is well known that certain components in Raney alloys, e.g., NiAl or NiAla, are difficult to dissolve with NaOH. However, they can be dissolved by aqueous solutions of a-hydroxy acids. Selective elimination of Al, together with the removal of disordered Ni results in an improved precursor Ni catalyst, denoted as the acid-treated RNi (RNiA). Thus, treatment of a conventional RNiH (6% Al) with a solution of glycolic acid (GA) or TA at pH 3.5 and 100"C yields RNiA(GA) or RNiA(TA) with an Al content less than 3%. "Soft" TA modification (pH 5 0"C) does not eliminate Al, but nevertheless gives MNi with a better e.d.a. thain RNiH (Table 1). The optimum modifying conditions stated in the early studies (pH 3.5-5 100 C) thus not only provide the favorable adsorption species (i.e., TAHNa) but also partly remove the N-regions by corrosion with acid (a one pot preparation of TA-MRNiA). 

ANTIMONOUS BROMIDE (7789-61-9) BfjSb Decomposed by light, air, and alcohol. Contact with moist air, water, steam, or alcohol produces corrosive hydrobromic acid and antimony trioxide. The aqueous solution is and acid. Violent reaction with bases, amines, amides, and inorganic hydroxides potassium, sodium. On small fires, use dry chemical powder (such as Purple-K-Powder), dry sand, or CO2 extinguishers. 

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