INHIBITORS OF METAL CORROSION

Abstract

The present invention relates to a composition of at least one sulfonic acid in combination with an effective amount of at least one nitrosyl compound, acting as inhibitor of corrosion of metals by said at least one sulfonic acid.

Claims

1. Use of at least one compound of general formula (1): in which X is chosen from: H; NO; a linear or branched alkyl radical R comprising from 1 to 6 carbon atoms; an aryl radical Ar which is optionally substituted, in particular by at least one alkyl radical R; a radical SO.sub.2-G, in which G represents H, OH, R, OR, OM, Ar, OAr, NH.sub.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, preferably an alkali metal or alkaline earth metal cation; and a radical CO-G, in which G is as defined above, for limiting, or even preventing, the corrosion of metals by sulfonic acids.

2. Use according to claim 1, in which X represents SO.sub.2-G, preferably SO.sub.2-G in which -G represents OH or R, R representing an alkyl radical, preferably the methyl radical.

3. Use according to claim 1, wherein the sulfonic acid is an acid of formula RSO.sub.3H, in which R represents a linear or branched saturated hydrocarbon-based chain comprising from 1 to 4 carbon atoms, optionally entirely or partially substituted by one or more identical or different halogen atoms, or an aryl radical optionally substituted by a linear or branched saturated hydrocarbon-based chain comprising from 1 to 4 carbon atoms, optionally entirely or partially substituted by one or more identical or different halogen atoms.

4. Use according to claim 1, wherein the sulfonic acid is 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, and mixtures of two or more thereof in any proportions, preferably the sulfonic acid is chosen from methanesulfonic acid, ethanesulfonic acid, trifluoromethanesulfonic acid and para-toluenesulfonic acid, entirely preferably the sulfonic acid is methanesulfonic acid.

5. Composition, in the form of an aqueous formulation, comprising at least one compound of formula (1) as defined in claim 1 and at least one sulfonic acid.

6. Composition according to claim 5, wherein the amount of compound(s) of formula (1) is between 1 ppm and 10%, preferably between 5 ppm and 1000 ppm, more preferably still between 10 ppm and 800 ppm, by weight relative to the total weight of the composition.

7. Composition according to claim 5, comprising from 0.01% to 100% by weight of sulfonic acid(s) in combination with at least one corrosion inhibitor of formula (1), the remainder of the composition comprising a solvent and/or a diluant.

8. Composition according to claim 5, 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 and mixtures of two or more thereof in any proportions, preferably methanesulfonic acid, in combination with at least one corrosion-inhibiting compound of formula ONOX, in which X is chosen from H, NO, a linear or branched alkyl radical R comprising from 1 to 6 carbon atoms and a radical SO.sub.2-G or CO-G, in which G represents OH or R as defined above, the sulfonic acid and corrosion inhibitor combination representing from 0.05% to 90% by weight, in particular from 0.5% to 75% by weight, of the total weight of said composition, the remainder of the composition being water.

9. Composition according to claim 5, comprising methanesulfonic acid, nitrosylsulfuric acid and water.

10. Composition according to claim 5, also comprising one or more additives chosen from: solvents, hydrotropic agents or solubilizers, biocides, disinfectants (bromoacetic acid, peracetic acid, aqueous hydrogen peroxide, chlorine dioxide, chlorine, bromine and the like), rheological agents, texturing agents, thickeners, gelling agents, complexing agents; organic or inorganic acids; flame retardants, preservatives, anionic, cationic, nonionic or amphoteric surfactants (such as ethoxylated alcohols and/or amines, alkyl and/or aryl sulfonates), emulsifiers, detergents, soaps, and the like, foaming agents, antifoams, antifreezes (for example ethylene glycol, propylene glycol, and the like), dyes, pigments; and fragrances, odorizing agents.

11. Process for protecting metals from corrosion by sulfonic acids, in particular metals and alloys which can be passivated, characterized in that the sulfonic acid coming into contact with said metals is a composition according to claim 5.

12. Process according to claim 11, 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.

13. Use of a composition according to claim 5 for storage, catalytic reactions or else cleaning, descaling, detergency, stripping, disinfection, galvanoplasty, plating, and the like, at temperatures ranging from 10 C. to 200 C., preferably from 0 C. to 160 C.

14. Use according to claim 13, for the stripping, 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 else in oil and gas operations where acid solutions are necessary for dissolving underground rocks, in particular carbonate-based rocks.

15. Use according to claim 13, for limiting, or even preventing, the corrosion of containers, barrels, tanks, receptacles, reactors, fermenters, lines, pipes, tubes, valves, in which at least one sulfonic acid is stored or conveyed.

16. Composition according to claim 5 wherein the sulfonic acid is alkanesulfonic acid.

17. Composition according to claim 5 wherein the sulfonic acid is MSA.

Description

EXAMPLE 1

Protocols for Electrochemical Tests

[0089] The electrochemical test is carried out using a conventional 3-electrode assembly (reference electrode (saturated calomel electrode SCE), working electrode made of the material to be studied and counter electrode made of platinum) connected to a BIOLOGIC VMP3 or EGG 273A potentiostat.

[0090] The test specimen of material to be tested is polished with P1000 abrasive paper in order to have a reproducible initial state, then left in the open air for at least 24 hours.

[0091] The working electrode is installed in a rotary system which makes it possible to set the rotation speed: the rotation speed is set at 1000 revolutions per minute.

[0092] Several types of test using this assembly were used during this study: [0093] Potentiokinetic or voltammetric) sweep I=f(E): variation of the potential E of the material and measurement of the current I between the material and the counter electrode makes it possible to estimate the behaviour of the material in the medium: quality of the passive layer, estimation of the corrosion rate (Tafel method at free corrosion potential and direct reading of the current measured at other potentials), etc. [0094] Monitoring the rest potential (or potential-time curve) of the material as a function of time E=f(t): monitoring the rest potential of a stainless material makes it possible to determine if the material is passive (negligible corrosion) or active (passive layer destroyed, significant corrosion), as long as the potentiokinetic polarization curve has been plotted beforehand. This type of test also makes it possible to monitor the behaviour of the material as a function of the conditions present in the medium: influence of deaeration, of temperature, of addition of inhibitors, etc.

EXAMPLE 2

Electrochemical Test Showing the Persistence of the Effect of the Inhibitor

[0095] The long-lasting effect of the inhibition by NHS in 70% MSA (Scaleva, Arkema) is demonstrated by monitoring the corrosion potential as a function of time at 40 C.

[0096] A test specimen of stainless steel 316L, of dimensions 35233 mm is in the standard state (polished P320 and passivated with air for at least 24 hours). [0097] During the immersion in 70% MSA at 40 C., the test specimen of stainless steel 316L depassivates immediately (potential of approximately 250 mV/SCE). [0098] The addition of 400 ppm of NHS into the medium passivates the stainless steel 316L of the test specimen: the potential becomes greater than 500 mV/SCE. [0099] After 21 days in these conditions, the 316L is still passive (potential greater than 500 mV/SCE),

[0100] FIG. 1 presents the passivation curve as a function of time: at the time t=0, the stainless steel 316L test specimen is immersed in a 70% MSA solution (Scaleva, Arkema) at 40 C. The stainless steel 316L becomes active as soon as it is immersed. At t=1200 seconds, 400 ppm of NHS (via a solution at approximately 60% of NHS in sulfuric acid) are added by means of an automatic micropipette to the acid solution at 40 C. The stainless steel 316L passivates immediately.

[0101] The nitrosylsulfonic acid used here is a solution at 60% by weight in sulfuric acid, prepared by sparging a 1/1 stoichiometric mixture of nitric oxide (NO) and of nitrogen dioxide (NO.sub.2) (70 g and 110 g, respectively), in 830 g of oleum (mixture of H.sub.2SO.sub.4/SO.sub.3: 77/23 by weight).

[0102] After 21 days, the steel test specimen is still passivated, indicating an absence of corrosion, even after this period of time.

EXAMPLE 3

Persistence, of the Inhibitory Effect Despite Worsening of the Test Conditions (Temperature Effect: 90 C.)

[0103] This test consists in monitoring the corrosion potential as a function of time: [0104] The freshly polished sample of stainless steel 316L is immersed in 70% MSA Scaleva+100 ppm of NHS at 40 C.: the sample passivates immediately. [0105] The temperature of the medium is gradually increased by increments of 10 C.: after 5 days, the medium is at 90 C.: the stainless steel 316L is still passive. [0106] After 460 hours (approximately 19 days), the sample is still passive.