Corrosives inorganic acids

Processes involving less corrosive organic acid such as carbolic, cre-sylic, salicylic and many others, are satisfactorily catered for by the nonmolybdenum steels. This also applies to the less corrosive inorganic acids such as boric, nitrous, and carbonic and silicic. 

Chapter 10 Corrosives Inorganic Acids Strength and Concentration pH... 

The most chemical-resistant plastic commercially available today is tetrafluoroethylene or TFE (Teflon). This thermoplastic is practically unaffected by all alkahes and acids except fluorine and chlorine gas at elevated temperatures and molten metals. It retains its properties up to 260°C (500°F). Chlorotrifluoroethylene or CTFE (Kel-F, Plaskon) also possesses excellent corrosion resistance to almost all acids and alkalies up to 180°C (350°F). A Teflon derivative has been developed from the copolymerization of tetrafluoroethylene and hexafluoropropylene. This resin, FEP, has similar properties to TFE except that it is not recommended for continuous exposures at temperatures above 200°C (400°F). Also, FEP can be extruded on conventional extrusion equipment, while TFE parts must be made by comphcated powder-metallurgy techniques. Another version is poly-vinylidene fluoride, or PVF2 (Kynar), which has excellent resistance to alkahes and acids to 150°C (300°F). It can be extruded. A more recent development is a copolymer of CTFE and ethylene (Halar). This material has excellent resistance to strong inorganic acids, bases, and salts up to 150°C. It also can be extruded. 

Most acids are corrosive to aluminium-base materials. The oxidising action of nitric acid at concentrations above about 80%, however, causes passivation of aluminium. Very dilute and very concentrated sulphuric acid dissolves aluminium only slowly. Figures 4.4 and 4.5 give corrosion data at various concentrations for these two acids. The corrosion rates of aluminium in other inorganic acids in dilute solution are shown in Fig. 4.6. Boric acid also exerts little attack on aluminium, while a mixture of chromic and phosphoric acids can be used for the quantitative removal of corrosion products from aluminium without attacking the metal. 

Inorganic acids, bases, and salts with pH values <4 and >9 are not compatible with aluminum. Pitting corrosion of aluminum can occur when it comes in contact with salt water and copper halide salts. 

Inorganic acids have similar acute toxic properties corrosive action on the skin, the respiratory tract, and especially the eyes where corneal damage may occur. Severe exposures may cause blindness, pulmonary edema, and even death. The onset of symptoms may be delayed for several hours after exposure. Prolonged exposures to low concentrations produce chronic effects such as tooth erosion, chronic bronchitis, and photosensitization of the skin (J >2, ). 

One common observation in patents and fundamental studies is that an acidic support promotes the selectivity. H202 is more stable in acid medium, but a strong acid could create problems of corrosion and further treatment of the solution. One of the motivations for the use of acidic supports was thus the reduction of the required concentration of inorganic acids in solution and hence minimization of... 

Current treatment solutions containing corrosive inorganic salts usually also contain corrosion inhibitors such as sodium dichromate or ammonium thiocyanate or are formulated to a more neutral pH (60). However, soluble-salt-treated wood in contact with metals should not be exposed to high relative humidities for prolonged periods. The treatment chemicals can attack and deteriorate metal fasteners. The corrosion products in turn deteriorate the wood. For example, under humid conditions, ammonium sulfate will attack the zinc and iron of galvanized punched-steel nail plates used in trusses (58). Alkaline and acidic areas are developed in the wood next to the attacked metal fastener, and cause degradation of the wood (58,63). 

It is well known that anhydrous nonoxidizing inorganic acids such as hydrogen chloride and hydrogen bromide do not dissolve metals. These two compounds are stored in steel cylinders without any appreciable corrosion of the metal. The same was true of anhydrous hydrogen fluoride that was stored and delivered in steel cylinders for the past seven decades. 

Some other unsuitable additives in LC/MS include surfactants/detergents and inorganic acids (sulfuric acid or phosphoric acid). The former additives tend to suppress the ionization of other compounds, while the latter can cause corrosion of metal parts in the source. As an ion-pairing agent, trifluoroacetic acid (TEA) reduces ESI signals in the positive ion mode and may completely suppress ionization in the negative ion mode. TEA is often used for peptides and protein analysis with a level of less than 0.1 %. 

The refiner s position on inorganic solids and salt removal is that as much of these contaminants (as is cost-effective) should be removed from the incoming crude oil into the wash water by the desalting process. Excess chloride salts become catalyst poisons that promote excessive catalyst consumption or reduce conversion in the cracking and treating processes. Chloride salts also compromise the reliability of refinery overheads where, because of hydrolysis upon heating, they form highly corrosive hydrochloric acid in the overhead system. (The refinery overhead is the equipment, such... 

In some cases, inorganic acid ( e.g., phosphoric acid) and organic acid (e.g., phenolsulfonic acid) are mixed with each other and used as a catalyst. Acid remaining in the final foam causes acidity of the foam. To minimize corrosion of the metal in contact with the foam the use of organic acid catal) t is preferable. 

Chemical/Pharmaceutical/Other Class Inorganic acid Corrosive... 

Synonyms Anhydrous hydroiodic acid Hydrogen iodide Hydrogen monoiodide Chemical/Pharmaceutical/Other Class Inorganic acid Corrosive Chemical Formula HI... 

Chemical/Pharmaceutical/Other Class Strong inorganic acid Corrosive agent... 

The presence of inorganic acids in distillate fuels, resulting from refinery treatment, is unlikely. However, some specifications for these fuels still include limiting clauses for total acidity and inorganic acidity as a check against possible corrosion of metal equipment in contact with the fuel. Inorganic acidity should in any case be entirely absent. 

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