Pickling, of steels

Pickling agent Pickling of steel Pickling solutions Pick s disease Pidoram [1918-02-1]... 

In situations such as the acid pickling of steel or the use of steel pipes to handle sour oil streams, the use of suitable inhibitors can give a significant reduction in hydrogen entry. In this context it is important to emphasise that the efficiency of an inhibitor in reducing hydrogen entry is not the same as its efficiency in reducing corrosion. Thus arsenic and antimony compounds... 

About 3 billion kilograms of hydrochloric acid are produced each year, mostly as a by-product of the plastics industry. The largest single use of hydrochloric acid is the pickling of steel. The pickling process removes iron(III) oxide (FC2 O3, rust) from the surface of the metal. About a third of all hydrochloric acid is used to produce other chemicals, mostly ionic compounds. Other strong acids have specialized applications in indushy and research laboratories, but none approaches the importance of sulfuric, nitric, and hydrochloric acids. 

Iron(II) sulphate is a by-product in many industrial processes, such as the manufacture of titanium dioxide, the pickling of steel sheet before galvanising and the reduction of aromatic nitro compounds to amines using iron catalysts. Conversion of waste iron (II) salts to usable iron oxide pigments, where the quality requirements are not too stringent, is therefore a useful proposition, since it uses up chemicals that would otherwise be regarded as waste products. 

Sulfuric acid is used in large quantities in the pickling of steel to remove oxide coatings by dissolving them. Another large use of sulfuric acid involves its reaction with ammonia obtained in the conversion of coal to coke ... 

Hydrochloric acid, HCI, is used in the pickling of steel and other metals to remove oxide layers on the surface. 

Derivation (1) By-product from the pickling of steel and many chemical operations, (2) by action of dilute sulfuric acid and iron, (3) oxidation of pyrites in air followed by leaching and treatment with scrap iron. 

Design a plant for the recovery of ferrous sulfate from the waste pickle resulting from the pickling of steel in a galvanizing plant. 

Corrosion reactions taking place in acidic environments give off hydrogen. Similarly, chemical surface treatments such as pickling of steel, or phosphatizing under acidic conditions produce hydrogen at the metal surface. 

In practice, inhibitors are often defined according to their field of application. In aqueous environments, inhibitors for acid environments are typically used to minimize metal corrosion during pickling of steel, an operation that removes oxide scales by dissolution in an acid. In the petroleum industry, large quantities of inhibitors for acid environments are used to avoid corrosion of drilling equipment. Inhibitors for neutral environments are used above all for the protection of cooling-water circuits. Inhibitors not only reduce the rate of uniform corrosion, but they also serve to protect metals from localized corrosion and stress corrosion cracking [18]. 

This specification covers the requirements for the pickling of steel surfaces—removal of all mill scale, rust, and rust scale by chemical reaction, or by electrolysis, or by both. It is intended that the pickled surface shall be completely free of all scale, rust, and foreign matter. Furthermore, the surface shall be free of unreacted or harmful acid or alkali or smut. 

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