Pickling process

Instead of de-rusling, a pickling process may also be suft icieni, depending upon the surface condition of the sheets. 

In the pickling process, use countercurrent flow of rinse water use indirect methods for heating and pickling baths. 

The corrosive effects to be considered (mainly simple corrosion of metals) are, as would be expected from the edible nature of foodstuffs which are not excessively either acidic or basic but which may contain sulphur, less severe than those often encountered with inedible materials containing reactive substances. The importance of corrosive efiects where foodstuffs are concerned lies not so much in the action of the foodstuffs on the metal involved as in the resultant metal contamination of the foodstuff itself, which may give rise to off-flavours, in the acceleration of other undesirable changes (by the Maillard reaction for example), and in the possible formation of toxic metallic salts. Metal ions generally have threshold values of content for incipient taste effect in different liquid foodstuffs. Except in the case of the manufacture of fruit juices and pickles, process plant failure through corrosion must be rare. Nevertheless all foodstuffs, particularly liquid ones, should be regarded as potentially corrosive and capable of metal pick-up which may be undesirable. 

With few exceptions it is more efficient and economical to use at least two different pretreatments, i.e. degreasing processes which deal with a) and b), and pickling processes which remove oxide and corrosion films. Degreasing comes first, as pickling processes fail on hydrophobic surfaces. 

Probably the major use of inhibitors in acid solutions is in pickling processes. The chief requirements of the inhibitor are that it should not decompose during the life of the pickle, not increase hydrogen absorption by the metal... 

When dry material or a slurry has been filled, "pickling" is required, which means that the plate is stored in sulfuric acid for a short time. The material is soaked by the acid and transformed, at least partly, into lead sulfate (PbS04), as in the pastemixing process (Section 4.4.2.1). When minium is used, during the "pickling" process lead dioxide is also formed according to Eq. (4). 

Without the addition of corrosion inhibitors, acid cleaning or pickling processes to remove oxides and scales would result in severe corrosion of exposed metal surfaces. Acid corrosion is an electrochemical or redox process, and raising cleaning temperatures or acid strength (lowering the pH) increases the hydrogen ion concentration and consequently the rate of corrosion. 

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. 

Effluent-Free Pickling Process with Fluid Bed Hydrochloric... 

This pickling process is operated such that no wastewater is discharged from a hydrochloric acid... 

Laser cutting, welding, and hot working leave a discolored oxidized layer or scale on the surface of the worked steel. This must be removed in order to perform many of the surface finishing processes. The acid pickling process is used to remove the oxide or scale of metals and corrosion products, in which acids or acid mixtures are used. 

The roughened ends of the pipe are manually deburred with an air grinder. Then the pipes are straightened as necessary and transported to the acid pickling process. 

All pipes and fittings are transported to the pickling process in which an overhead crane is used to lower them into an acidic pickle liquor solution that chemically cleans and etches the black oxide surface layer resulting in a clean, rust-resistant pipe. 

In the hydrochloric acid pickling process, ferrous chloride can also be recovered as a by-product. 

Iron(II) sulfate in industrial scale is mostly produced in the pickling process as a by-product of the steel industry. It is obtained when the surface of steel is cleaned with dilute sulfuric acid to remove metal impurities. In the laboratory iron(II) sulfate heptahydrate may be prepared by dissolving iron in dilute sulfuric acid in a reducing atmosphere, followed by crystallization ... 

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