Acids corrosive action

Tellurium improves the machinability of copper and stainless steel, and its addition to lead decreases the corrosive action of sulfuric acid on lead and improves its strength and hardness. Tellurium is used as a basic ingredient in blasting caps, and is added to cast iron for chill control. Tellurium is used in ceramics. Bismuth telluride has been used in thermoelectric devices. 

Vessels and equipment must withstand the corrosive action of hydroduoric acid. For a high quaUty product the preferred materials for handling... 

Compound (1) decomposes to form dichloroacetyl chloride, which in the presence of water decomposes to dichloroacetic acid and hydrochloric acid (HCl) with consequent increases in the corrosive action of the solvent on metal surfaces. Compound (2) decomposes to yield phosgene, carbon monoxide, and hydrogen chloride with an increase in the corrosive action on metal surfaces. 

Stopping acid corrosion requires the following prevention and emergency action steps ... 

Sulphates, silicates, carbonates, colloids and certain organic compounds act as inhibitors if evenly distributed, and sodium silicate has been used as such in certain media. Nitrates tend to promote corrosion, especially in acid soil waters, due to cathodic de-polarisation and to the formation of soluble nitrates. Alkaline soils can cause serious corrosion with the formation of alkali plumbites which decompose to give (red) lead monoxide. Organic acids and carbon dioxide from rotting vegetable matter or manure also have a strong corrosive action. This is probably the explanation of phenol corrosion , which is not caused by phenol, but thought to be caused by decomposition of jute or hessian in applied protective layers. ... 

The corrosion of tin by nitric acid and its inhibition by n-alkylamines has been reportedThe action of perchloric acid on tin has been studied " and sulphuric acid corrosion inhibition by aniline, pyridine and their derivatives as well as sulphones, sulphoxides and sulphides described. Attack of tin by oxalic, citric and tartaric acids was found to be under the anodic control of the Sn salts in solution in oxygen free conditions . In a study of tin contaminated by up to 1200 ppm Sb, it was demonstrated that the modified surface chemistry catalysed the hydrogen evolution reaction in deaerated citric acid solution. 

Although halide ions are aggressive in near-neutral solutions they can be used to improve the action of inhibitors in acid corrosion (see Practice Acid Solutions). Variations exist among the halides, e.g. chloride ions favour the stress-corrosion cracking of Ti in methanol whereas iodide ions have an inhibitive action ... 

In addition to their concern regarding spray residues of the lead arsenate and organic types, canners whose fruits are sprayed with lime sulfur have reason for concern over the presence of sulfur in their canned products. The presence of elemental sulfur or simple compounds of reduced sulfur in canned foods, especially in those products having an acid character, is objectionable, not only because it may be the source of sulfide flavor and staining, but also because it may actively accelerate the formation of hydrogen by the corrosive action of the product on the container. 

In extreme cases irritant chemicals can have a corrosive action. Corrosive substances can attack and weaken materials of construction, as mentioned in Chapter 3. They can also attack living tissue (e.g. to cause skin ulceration and in severe cases chemical burns), kill cells and possibly predispose to secondary bacterial invasion. Thus while acute irritation is a local and reversible response, corrosion is irreversible destruction at the site of the contact. The outcome is influenced by the nature of the compound, the concentration, duration of exposure, the pH (see Figure 4.1) etc. Thus dilute mineral acids may be irritant whereas at higher concentrations they may cause corrosion. 

Mucus is produced by the mucus neck cells and by the surface epithelial cells of the stomach wall. A thick layer of mucus adheres to the wall of the stomach, forming the gastric mucosal barrier. The function of this barrier is to protect the gastric mucosa from injury — specifically, from the corrosive actions of HCl and pepsin. Together with bicarbonate ion released into the lumen of the stomach, mucus neutralizes the acid and maintains the mucosal surface at a nearly neutral pH. 

Phosphine in small quantities in hydrogen containing over I per cent, of oxygen attacks copper, producing an acid liquid which has a most corrosive action on fabric. However, it does not appear under these circumstances to have any action on aluminium or zinc consequently any metal parts inside the envelope of an airship should be of aluminium. Phosphine under the above conditions attacks hemp and other textiles which have been treated with copper compounds, but it does not appear to have any action on fabrics free from copper compounds or copper or brass fastenings. 

Workers exposed to an airborne fluoride concentration of 5mg/m complained of eye and respiratory tract irritation and nausea. The lethal oral dose of sodium fluoride for humans has been estimated to be 32-65 mg F/kg of body weight. Effects from ingestion are diffuse abdominal pain, diarrhea, and vomiting excessive salivation, thirst, and perspiration painful spasms of the limbs and sometimes albuminuria." Gastrointestinal effects produced after the acute ingestion of toxic amounts of fluoride likely arise from the corrosive action of hydrofluoric acid, which is produced within the acidic environment of the stomach. Cardiac arrest after accidental exposure to high levels of fluoride has been attributed to the development of hypocalcemia and/or hyperkalemia. ... 

Cylinder and piston ring wear have been observed when using alcohol fuels. Metal loss could be due to wear caused by removal of the lubricating oil film by liquid alcohol during cold starting or by the corrosive action of formic acid or other acids formed during the combustion process. Use of more corrosion- and wear-resistant metal alloys in engine construction have helped resolve this problem. 

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, ). 

It was found (according to Canright [13]) that the addition of small amounts of hydrogen fluoride to nitric acid considerably reduces its corrosive action on aluminium and stainless steel since these metals become coated with a layer of fluorides. 

Just because an acid or base is strong doesn t mean a solution of that acid or base is corrosive. The corrosive action of an acidic solution is caused by the hydronium ions rather than by the acid that generated those hydronium ions. Similarly, the corrosive action of a basic solution results from the hydroxide ions it contains, regardless of the base that generated those hydroxide ions. A very dilute solution of a strong acid or a strong base may have litde corrosive action because in such solutions there are only a few hydronium or hydroxide ions. (Almost all the molecules of the strong acid or base break up into ions,... 

Was this your answer Because H2S04 is a strong acid, it readily forms hydronium ions when dissolved in water. Hydronium ions are responsible for the corrosive action. 

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