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. 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.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; 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.sub.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.

Description

EXAMPLE 1

Protocols for Electrochemical Tests

(1) 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.

(2) 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.

(3) 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.

(4) Several types of test using this assembly were used during this study: 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. 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

(5) 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.

(6) A test specimen of stainless steel 316L, of dimensions 35×23×3 mm is in the standard state (polished P320 and passivated with air for at least 24 hours). During the immersion in 70% MSA at 40° C., the test specimen of stainless steel 316L depassivates immediately (potential of approximately −250 mV/SCE). 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. After 21 days in these conditions, the 316L is still passive (potential greater than 500 mV/SCE),

(7) 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.

(8) 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).

(9) 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.)

(10) This test consists in monitoring the corrosion potential as a function of time: 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. 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. After 460 hours (approximately 19 days), the sample is still passive.