the chemical or electrochemical removal of the very thin oxide films that form on the surfaces of metal articles during storage or transportation. Pickling is done to clean and activate metal surfaces for passivation, oxidation, and electroplating. In pickling there is slight etching of the metal layer, which promotes adhesion of the electroplated coating. Pickling uses dilute sulfuric, hydrochloric, or nitric acid, as well as dilute solutions of potassium or sodium cyanide.

(1) The preserving of vegetables by means of lactic acid fermentation (primarily cabbage but also eggplant and mixed vegetables). Lactic acid is formed during this process. The lactic acid, together with salt, preserves the vegetables. Pickled products should be kept at a temperature of 0°-2°C.

(2) In the leather and fur industries, the steeping of hides in a solution of water and coarse-grained oat or barley flour; salt and sometimes bran is added. As a result of pickling, some of the transverse bonds are destroyed in the collagen, causing a significant division of the large structural elements (bundles) into smaller elements (fibers and fibrils). This process gives pickled hide its great ductility. Although the keratins in the hair shaft are resistant to the pickling action, hair follicles that are not completely keratinized are weakened by prolonged action of the pickling solution. For this reason, pickling is used in preparation for depilation (for example, in the production of rawhide). The process of pickling is lengthy and labor intensive; it is also difficult to determine the right time to stop the process. As a result, its use is limited to the currying of squirrel and karakul skins.

a method of preserving food products that is based on the action of acetic acid, which in certain concentrations (and particularly in the presence of salt) suppresses the vital activity of many microorganisms. The concentrations of acetic acid acceptable with regard to flavor do not under certain circumstances protect the product from the development of some molds, yeasts, and bacteria. Therefore, to preserve the products, salt is added, or the product is pasteurized or is stored at a low temperature (no higher than 4°C) in a closed airtight container.

Fruits, vegetables, mushrooms, and fish are pickled. The products are prepared by being sorted according to quality and size, washed, and in many instances peeled and sliced. They are then pickled either in a raw state (some fruits and vegetables) or after being boiled thoroughly (blanched). Next, they are put into a container, and then filled up with the pickle, which has been cooked with sugar, spices, salt (no salt for fruits), and vinegar.

the treatment of semifinished leather and fur products with a solution containing acid and salt. Pickling, a method of preservation, loosens the fine structure of collagen, separates the microstructure of the derma, and endows the semifinished product (without swelling) with the acidity needed before chrome tannage. A solution, or pickle, containing H₂SO₄ and NaCl is most commonly used.

in the leather and fur industry, the preparation of an article for dyeing. This process increases the fur filaments’ receptivity to the dyestuff, changes the shade, and improves the dye’s fastness against light and friction. Pickling in the fur industry involves treating the hair coat with compounds of chromium, copper, iron, and other heavy metals. In the leather industry, the hides are pickled with tannins prior to dyeing.

in the leather industry, the treatment of hides with concentrated solutions of ammonium sulfate, sodium sulfate, and sodium chloride. The treatment improves the permeability of the hides to tanning agents. Pickling is also used in processing rawhide and the kid leather used for shoes.