Abstract: An aqueous cleaning solution for removing rouging deposits on media-contacted surfaces of stainless steels comprises a first component and a second component. The first component is an alkali sulfite and the second component is an alkali formate, wherein the concentrations thereof are adjusted in such manner that formate is present in a molar ratio of 1.5 to 4.2 relative to sulfite, and that the pH value of the cleaning solution is 4.0 to 4.8. For preparing the aqueous cleaning solution, an aqueous solution of an alkali hydroxide is provided initially, thereafter a first amount of concentrated aqueous formic acid is admixed in an excess in such manner that a pH value of 3.5 to 4.5 is established, then a second amount of solid alkali sulfite is admixed in accordance with the sulfite concentration to be established, thus resulting in a pH value of 5.5 to 6.5, and finally a third amount of concentrated aqueous formic acid is admixed until a pH value of 4.0 to 4.8 is attained.