The high-strength plated steel sheet of the present invention has a plated layer on the surface of a base steel sheet and contains predetermined steel components. The steel sheet includes, in the order from the interface of the base steel sheet and the plated layer towards the base steel sheet: a soft layer having a Vickers hardness that is 90% or less of the Vickers hardness at a portion t/4 of the base steel sheet, where t is a sheet thickness of the base steel sheet: and a hard layer containing martensite, bainite, and ferrite in predetermined ranges. The average depth D of the soft layer is 20 μm or greater, and the average depth d of an internal oxide layer is 4 μm or greater and smaller than D.

A process for chemical cleaning and corrosion inhibition of pipework, typically in closed loop systems, that avoids or significantly minimises the requirement for wastewater discharge where the system is first acidified using a mixture of cleaning agents capable of dissolving metal oxides. The method then precipitates any dissolved contaminants and separates the precipitate from the carrying fluid. Further elements of a combined corrosion inhibitor package are then added to any cleaning agent ions that remain in solution to develop a fully functional corrosion inhibition package to protect the metals of the system.

A cleaning agent comprising a polyacrylate terpolymer and a maleic olefin compound may be added to an aqueous system having a metal surface, such as a metal surface of a heat exchanger, in a concentration sufficient to remove fouling deposits from the metal surface in neutral or alkaline conditions. The removal of fouling deposits with the application of the cleaning agent may occur while the system is shut down or in service.

A cleaning agent comprising a polyacrylate terpolymer and a maleic olefin compound may be added to an aqueous system having a metal surface, such as a metal surface of a heat exchanger, in a concentration sufficient to remove fouling deposits from the metal surface in neutral or alkaline conditions. The removal of fouling deposits with the application of the cleaning agent may occur while the system is shut down or in service.

A corrosion inhibition package for use with an aqueous acid composition, said package comprising: a terpene; a cinnamaldehyde or a derivative thereof; at least one amphoteric surfactant; and a solvent. Also disclosed are compositions comprising said corrosion inhibitor package. Preferably, the corrosion inhibition package meets the environmental requirements for classification as yellow according to the Norwegian North Sea offshore drilling regulatory requirements.

A corrosion inhibition package for use with an aqueous acid composition, said package comprising: a terpene; a cinnamaldehyde or a derivative thereof; at least one amphoteric surfactant; and a solvent. Also disclosed are compositions comprising said corrosion inhibitor package. Preferably, the corrosion inhibition package meets the environmental requirements for classification as yellow according to the Norwegian North Sea offshore drilling regulatory requirements.

An inhibited hydrofluoric acid aqueous composition, said composition comprising: hydrofluoric acid in solution; and a weak base selected from the group consisting of: lysine, arginine, histidine, glutamine, asparagine, tryptophan, and tyrosine; wherein said weak base and hydrofluoric acid are present in a molar ratio of at least 1:1. Also disclosed is a mud acid using this inhibited acid composition.

An inhibition corrosion package for use with an acidic composition, where the package comprises a terpene component; a propargyl alcohol or derivative thereof; at least one amphoteric surfactant; and a solvent. Also disclosed are acidic compositions combining the corrosion inhibition package according to a preferred embodiment of the present invention for use in various industrial operations including but not limited to oil and gas operations. Also disclosed are methods of use of such compositions.

An inhibition corrosion package for use with an acidic composition, where the package comprises a terpene component; a propargyl alcohol or derivative thereof; at least one amphoteric surfactant; and a solvent. Also disclosed are acidic compositions combining the corrosion inhibition package according to a preferred embodiment of the present invention for use in various industrial operations including but not limited to oil and gas operations. Also disclosed are methods of use of such compositions.

Disclosed are an ionic liquid for pickling a stainless steel capable of rapidly removing oxide scale from the stainless steel at room temperature without using nitric acid or hydrofluoric acid and a method for pickling a stainless steel by using the same. The method for pickling a stainless steel according to an embodiment includes performing electrolytic pickling treatment by immersing a stainless steel in a pickling solution including an ionic liquid, wherein the ionic liquid comprises at least one of an imidazolium cation, a betainium cation, a sulfonium cation, a piperidinium cation, a phosphonium cation, an ammonium cation, a pyridium cation, a pyrrolidinium cation, and a morpholinium cation, as a cationic functional group, and at least one of a halide anion, a sulfonate anion, an alkylsulfate anion, a phosphinate anion, a salicylate anion, a nitrate anion, a tetrafluoroborate anion, a hexafluorophosphate anion, and a bistriflimide anion, as an anionic functional group.