Inhibitors of metal corrosion

A composition, in the form of an aqueous formulation, comprising at least one sulfonic acid and at least one compound of formula (1)

• O═N—OX (1)
• in which X is chosen from:
• NO;
• a linear or branched alkyl radical R comprising from 1 to 6 carbon atoms;
• an aryl radical Ar which is optionally substituted by at least one alkyl radical R;
• a radical —SO2-G, in which G represents H, OH, R, OR, OM, Ar, OAr, NH2, NHR and NRR′, in which R and Ar are as defined above, R′ represents a linear or branched alkyl radical comprising from 1 to 6 carbon atoms and M represents a monovalent or bivalent metal cation;
• and
• a radical —CO-G, in which G is as defined above,
• wherein the compound is in an amount effective for limiting, or even preventing, the corrosion of metals by sulfonic acids.