Inhibitors of metal corrosion

1. 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 —SO 2 -G, in which G represents H, OH, R, OR, OM, Ar, OAr, NH 2 , 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.

2. The composition according to claim 1 , wherein the amount of compound(s) of formula (1) is between 1 ppm and 10%, by weight relative to the total weight of the composition.

3. The composition according to claim 1 , comprising from 0.01% to 100% by weight of sulfonic acid(s) in combination with at least one compound of formula (1), and the remainder of the composition comprising a solvent and/or a diluant.

4. The composition according to claim 1 , comprising at least one sulfonic acid chosen from methanesulfonic acid, ethanesulfonic acid, n-propanesulfonic acid, iso-propanesulfonic acid, n-butanesulfonic acid, iso-butanesulfonic acid, sec-butanesulfonic acid, tert-butanesulfonic acid, trifluoromethanesulfonic acid, para-toluenesulfonic acid, benzenesulfonic acid or mixtures thereof and where the compound of formula O═N—OX includes X chosen from NO, a linear or branched alkyl radical R comprising from 1 to 6 carbon atoms and a radical —SO 2 -G or —CO-G, in which G represents OH or R as defined above, and wherein the sulfonic acid and corrosion inhibitor are present in amounts from 0.05% to 90% by weight of the total weight of said composition, the remainder of the composition being water.

5. The composition according to claim 1 , comprising methanesulfonic acid, nitrosylsulfuric acid and water.

6. The composition according to claim 1 , also comprising one or more additives chosen from:

solvents, hydrotropic agents or solubilizers,

biocides, disinfectants,

rheological agents, texturing agents, thickeners, gelling agents,

complexing agents;

organic or inorganic acids;

flame retardants,

preservatives,

anionic, cationic, non-ionic or amphoteric surfactants, emulsifiers, detergents, soaps,

foaming agents, antifoams,

antifreezes,

dyes, pigments; and

fragrances, odorizing agents.

7. The composition according to claim 1 wherein the sulfonic acid is alkanesulfonic acid.

8. The composition according to claim 1 wherein the sulfonic acid is MSA.

9. A process for protecting metals from corrosion by sulfonic acids, in particular metals and alloys which can be passivated, comprising contacting said metals with the composition according to claim 1 .

10. The process according to claim 9 , in which the metal is chosen from iron-based or nickel-based stainless steels or alloys, titanium, copper, aluminium, molybdenum, manganese, lead and alloys thereof, and also the pairs (in the galvanic sense) of these metals or alloys.

11. In a process for storage, catalytic reactions cleaning, descaling, detergency, stripping, disinfection, galvanoplasty, or plating where metal is contacted with acid at temperatures ranging from −10° C. to 200° C. where the improvement comprises contacting the metal with the composition according to claim 1 .

12. The process according to claim 11 , includes, cleaning, descaling and detergency of inorganic and/or organic soiling in food-processing industries such as dairies, cheese-making facilities, grocery and meat product packaging, breweries, and also the stripping, cleaning and descaling of inorganic residues in cement works, in all domains where it is necessary and desirable to eliminate rust, or oil and gas operations where acid solutions are necessary for dissolving underground rocks, in particular carbonate-based rocks.

13. The process according to claim 11 , where the metal includes containers, barrels, tanks, receptacles, reactors, fermenters, lines, pipes, tubes, valves, in which at least one sulfonic acid is stored or conveyed.