GB2204864A

GB2204864A - Corrosion inhibition

Info

Publication number: GB2204864A
Application number: GB08710195A
Authority: GB
Inventors: William Neagle
Original assignee: Ciba Geigy AG
Current assignee: Novartis AG
Priority date: 1987-04-29
Filing date: 1987-04-29
Publication date: 1988-11-23
Also published as: FR2614630A1; DE3814055A1; JPS63290284A; GB8710195D0

Description

CORROSION INHIBITION 220d864 The present invention relates to methods for

inhibiting the corrosion of copper; and alloys containing copper; and to compositions in contact with copper and its alloys for inhibiting corrosion.

It is well established that surfaces of copper.are susceptible to corrosion, when such surfaces come into contact with aqueous or nonaqueous media. Furthermore, the products of such copper corrosion may catalyse the decomposition of any organic media in contact with the corroding copper surface and may galvanically induce the corrosion of other metals, eg iron or aluminium, which may be present.

Many compounds of widely different structures have been proposed as copper corrosion inhibitors for use in media such as aqueous systems or functional fluids.

Amongst many others, one type of compound which hasbeen found to be effective comprises the Schiff bases derived from the condensation of an aromatic amine and an aromatic aldehyde. In Surface Coatings and Technology 27, 175-86 (1986), N-(2-mercaptophenyl)salicylidenimine is described as a corrosion inhibitor for copper in aqueous alcoholic media, while in Surface Coatings and Technology 29, 141-151 (1986) the same molecule and its analogues are described as corrosion inhibitors for copper and its alloys in acid media.

In earlier publicationsp Schiff bases have been described as metal corrosion inhibitors in a number of systems. Thus in J. Electrochem. Soc. India 32, 397-401 (1983) N,NI-bis(2-hydroxybenzylidene)ethylehediamine and N,NI-bis(4-methoxybenzylidene)ethylenediamine are described as corrosion inhibitors for zinc in sulphamic acid; in US 3865739 an alkylidenimino thiadiazole inhibitor is disclosed; in GB 1434354 the azomethine derived from the condensation of cinnamaldehyde and Zr- amino-capronitrile is described as an inhibitor for steel in hydrochloric acid.

Against this varied background art, suggesting metal corrosion-inhibition by Schiff bases, we have found, surprisingly, that mixtures of Schiff base precursors provide outstanding copper corrosion inhibition in various media e.g. functional fluids and aqueous systems.

Accordingly, the present invention provides a method of inhibiting the corrosion of copper or of a metal containing copper, comprising contacting the surface of the copper, or copper containing alloy with a corrosion-inhibiting amount of a mixture of a compound having the formula A: Rl-C=O H A wherein R1 is Cl-C19 straight- or branched chain alkyl, C5-C12 cycloalkyl, C7-C13 aralkyl, optionally substituted C6P C10 or C14 aryl, a monocyclic heterocyclic residue having up to 5 ring carbon atoms or a residue of formula I:

-(CB2)n-CHO I where n=1-6:

and a compound having the formula B R2-NH2 B where R2 is Cl-C19 straight or branched chain alkyl, C5-C12 cycloalkyl, C7-C13 aralkyl, optionally substituted C6r C10 or C14 aryl, a monocyclic heterocyclic residue having up to 5 ring carbon atoms or a residue of the formula II: -(CH2)MNH2 II where m=1-6.

When R1 or R2 are Cj-Cjq alkyl groups, they may be straightor branched chain eg methyl, ethyl, n-propyl, iso-propyl, n-butyl, sec-butyl, npentyl, n-hexyl, n-heptyl, n-octyl, 2-ethylhexyl, n-nonyl, n-decyl, ndodecyl, n-tridecyl, n-pentadecyl, n-heptadecyl or n-nonadecyl.

As C5-C12 - cycloalkyl groups R1 or R2 may be eg cyclopentyl, cyclohexylt cyclooctyl, cyclodecyl, adamantyl or cyclododecyl.

As C7-C13 - Aralkyl groups R1 or R2 may be benzyl, 2-phenylethyl, benzhydryl or naphthylmethyl.

C6j, C10 or C14 Aryl groups R1 or R2 are phenyl, naphthyl or anthracenyl. Optional substituents in these aryl groups are eg hydroxyl, thiol, carbonyl, carboxyl or sulphoxyl.

As heterocyclic residues, R1 and R2 may be e.g. pyridyl, furfuryl or thiophene.

Preferred compounds of formula A are those having the formula A(i):

x CH of 0 A(i) where X is hydrogent hydroxyl, thiol or a group CR3 where R3 is n 0 hydrogen or hydroxyl.

Other preferred compounds are those of formula A(ii):

OHC(CH2)nCHO A(ii) where n=1-6 Preferred compounds of formula B are those having the formula B(i):

Y NH2 B(i) where Y is hydrogen, amino, hydroxyl, thiol, carboxyl or sulphoxyl.

Specific example of compounds of formula I for use in the compositions of the compounds include. Acetaldehyde Propionaldehyde Butyraldehyde Isobutyraldehyde 2-ethylbutyraldehyde Valeraldehyde Isovaleraldehyde Hexanoaldehyde Heptanaldehyde Octyl aldehyde Nonyl aldehyde Decyl aldehyde Undecyl aldehyde Dodecyl aldehyde Tetradecyl aldehyd Pentadecyl aldehyde Hexadecyl aldehyde Octadecyl aldehyde Eicosyl aldehyde Cyclopentanecarboxaldehyde Cylohexanecarboxaldehyde Cyclooctanecarboxaldehyde Cyclododecylcarboxaldehyde Phenylacetaldehyde 3phenylpropionaldehyde Benzhydryl carboxaldehyde 1 w Napthylacetaldehyde Benzaldehyde Salicaldehyde 3-Hydroxybenzaldehyde 4- Hydroxybenzaldehyde 2-Mercaptobenzaldehyde 3-mercaptobenzaldehyde 4- Mercaptobenzaldehyde Phthalaldehyde Isophthalaldehyde Terephthalaldehyde 2-Carboxybenzaldehyde 4-Carboxybenzaldehyde 2-sulphobenzaldehyde 4- sulphobenzaldehyde 1-Naphthaldehyde 2-Naphthaldehyde 2-Hydroxy-l- napthaldehyde 2-Mercapto-l-napthaldehyde 1-Anthracenaldehyde 2- Anthracenaldehyde 2-Hydroxy-l-anthracenaldehyde Malonaldehyde Succinaldehyde Glutaraldehyde Adipic aldehyde 1,5-Heptan-dicarboxaldehyde 1,6-Hexan-dicarboxaldehyde Furfural Thiophene-2-carboxaldehyde 6 Specific examples of compounds of formula B include Methylamine Ethylamine Propylamine Isopropylamine n-Butylamine sec-Butylamine tert- Butylamine n-Amylamine tert-Amylamine n-Hexylamine n-Heptylamine n-Octylamine 2- Ethyl hexylamine n-Nonylamine n-Decylamine n-Undecylamine n-dodecylamine n-Tridecylamine n-Tetradecylamine 1-Hexadecylamine 1-Octadecylamine Cyclopentylamine Cyclohexylamine Cycloheptylamine Cyclooctylamine 1 - Adamantamine Cyclodexdecylamine Benzylamine 2-Phenylethylamine 4 C) Benzhydrylamine 3-Phenylpropylamine 4-Phenylbutylamine Napthylmethylamine Aniline 2-Hydroxyaniline 3-Hydroxyaniline 4- Hydroxyaniline 2-mercaptoaniline 3-mercaptoaniline 4-mercaptoaniline 2- aminobenzaldehyde Anthranilic acid 3-Aminobenzoic acid 4-Aminobenzoic acid Sulphanilic acid 2-aminobenzenesulfonic acid Dimethylamine 2-Diethylamine,3-Dipropylamine,4-Dibutylamine,S-Dipentylamine 1,6Dihexylamine o-Phenylenediamine m-Phenylenediamine p-Phenylenediamine 1Napthylamine 1-Amino-2-napthol 1-Amino-7-napthol 3-Amino-2-napthol 8 4-Aznino-l-napthol 8-Amino-2-napthol 3-Amino-2-napthoic acid 2-Amino-lnapthalenesulphonic acid 4-Amino-l-napthalenesulphonic acid 5-Amino-2napthalenesulphonic acid 8-Amino-2-napthalenesulphonic acid 3-Amino-2,7napthalenesulphonic acid 7-Amino-1,3-napthalenedisulphonic acid 1Aminoanthracene 2-Aminoanthracene 2-Aminopyridine 3-Aminopyridine The method of treating the metal surface may be by a variety of techniques. For example, the copper surface may be wrapped in a film impregnated with suitable amounts of the compounds of formula A and B, or the copper surface may be dipped into a solution eg an aqueous solution containing suitable amounts of compounds of formula A and B. More usually, however, the metal surface will be permanently in contact with a substrate which causes corrosion of the metal surface. In such cases the surfaces of copper-containing metals can be effectively inhibited against corrosion by adding a corrosion-inhibiting amount of a mixture of compounds of formulae A and B. The mixture in all the above methods may contain non-equimolar amounts of A and B, e.g. in a ratio of from 3:1 to 1:3, but preferably contains an equimolar composition.

The present invention, therefore, also provides a composition comprising a substrate in contact with copper, or a metal containing copper and a copper corrosion-inhibiting amount, - 9 preferably 0.001% to 5% by weight,-more preferably 0.01% to 1% based on total weight of the substrate, of a composition of compounds of formulae A and B as hereinbefore defined.

Examples of substrates which may be treated according to the present invention include functional fluids such as lubricants eg those having a mineral oil, poly-alpha olefin or synthetic carboxylic acid ester base; hydraulic fluids eg those based on mineral oils, phosphate esterst aqueous polyglycol/polyglycol ether mixtures or glycol systems; oil-in- water or water-in-oil systems; metal-working fluids having, as their base, mineral oil or aqueous systems; water- or aqueous glycol- or ethylene- or propylene glycol/methanol based engine coolant systems; transformer- or switch oils; as well as aqueous systems eg industrial cooling water; aqueous air-conditioning systems; steam-generating systems; sea-water evaporator systems; hydrostatic cookers; and aqueous closed circuit heating or refrigerant systems.

When a functional fluid substrate is a synthetic lubricant, examples thereof include lubricants based on a diester of a dibasic acid and a monohydric alcohol, for instance dioctyl sebacate or dinonyladipate; on a triester of trimethylolpropane and a monobasic acid or mixture of such acids, for instance trimethylol propane tripelargonate, trimethylolpropane tricaprylate or mixtures thereof; on a tetraester of pentaerythritol and a monobasic acid or mixture of such acids, for instance pentaerythritol tetracaprylate; or on complex esters derived from monobasic acids, dibasic acids and polyhydric alcohols, for instance a complex ester derived from trimethylol propane, caprylic acid and sebacic-acid; or of mixtures thereof.

- Other synthetic lubricants are those known to the art-skilled and described eg in "Schmiermittel-Taschenbuch" (Huethig Verlag, Heidelberg 1974). Especially suitable, apart from the preferred mineral oils are eg phosphates, glycols, polyglycols, polyalkylene glycols and poly-alpha olefins.

In order to improve various applicational properties, a functional fluid composition of the invention may also contain other additives such as, for oil-based systems, one or more of antioxidantsp metal deactivators, further corrosion or rust inhibitors, viscosity-index improvers, pourpoint depressants, dispersants/surfactants and/or anti-wear additives; and for aqueous-based systems, one or more of antioxidants, other corrosionand rust inhibitors, metal deactivators, extreme pressure- or anti-wear additives, complexing agents, precipitation inhibitors, biocides, buffering agents and/or anti-foams.

For oil-based systems, examples of other additives are: Examples of phenolic antioxidants 1. Alkylated Monophenols 2,6-Di-tert.-butylphenol 2tert.-butyl-4,6-dimethylphenol 2,6-Di-tert.-butyl-4-ethylphenol 2,6-Ditert.-butyl-4-n-butylphenol 2,6-Di-tert.-butyl-4-i-butylphenol 2,6-Dicyclopentyl-4-methylpheno1 2-(p-Methylcyclohexyl)-4,6-dimethylphenol 2,6Di-octadecyl-4-methylphenol 2,4,6-Tri-cyclohexylphenol 2,6-Di-tert.-butyl4-methoxymethylphenol 2. Alkylated Hydroquinones 2,6-Di-tert.-butyl-4methoxyphenol - 1 1 - e 2,5-Di-tert.-butyl-hydroquinone 2,5-Di-tert.-amyl-hydroquinone 2,6- diphenyl-4-octadecyloxyphenol 3. Hydroxylated Thiodiphenylethers 2,21Thio-bis-(6-tert.butyl-4-methylphenol) 2,21-Thio-bis-(4-octylphenol) 4,41Thio-bis-(6-tert.butyl-3-methylphenol) 4,41-Thio-bis-(6-tert.butyl-2methylphenol) 4. Alkylidene-Bisphenols 2r21-Methylene-bis-(6-tert.-butyl4-methylphenol) 2,21-Methylene-bis-(6-tert.-butyl-4-ethylphenol) 2,21Methylene-bis-(4-methyl-6-(.-methylcyclohexyl)-phenol) 2,21-Methylene-bis(4-methyl-6-cyclohexylphenol) 2.21-Methylene-bis-(6-nonyl-4-methylphenol) 2,21-Methylen e-bis-(4,6-di-tert.-butylphenol) 2,21-Ethylidene-bis(4,6-ditert.-butylphenol) 2,21-Ethylidene-bis-(6-tert.-butyl-4-isobutylphenol) 2, 21-Methylene-bis-(6-(o(,-methylbenzyl-4-nonylphenol) 2,21-Methylene-bis(6-(.,o(-dimethylbenzyl)-4-nonylphenol) 4,41-Methylene-bis-(6-tert.-butyl2-methylphenol) 1,11-Bis-(5-tert.-butyl-4-hydroxy-2-methylphenol)-butane 2y6'-Di-(3-tert.butyl-S-methyl-2-hydroxybenzyl)-4-methylphenol l,ly3-Tris(5-tert.butyl-4-hydroxy-2-methylphenyl)-3-n-dodecylmercaptobutane Ethyleneglycol-bis-[3,3-bis-(3'tert.-butyl-41-hydroxyphenyl)butyratel Di(3-tert.-butyl-4-hydroxy-5-methylphenyl)-dicyclopentadiene Di-[31-tert.butyl-21-hydroxy-51-methyl-benzyl)-6-tert.-butyl4-methyl-phenyllterephthalate cl 5. Benzyl Compounds 1,3,5-Tri-(3,5-di-tert.-butyl-4-hydroxybenzyl)-2,4, 6-trimethyl- benzene Di-(3,5-di-tert.-butyl-4-hydroxybenzyl)-sulfide Bis-(4-tert.butyl-3-hydroxy-2,6-dimethylbenzyl)dithiolterephthalate 1,3,5-Tris-(3,5di-tert.-butyl-4-hydroxybenzyl)-isocyanurate 1.3.5-Tris-(4-tert.-butyl-3hydroxy-2,6-dimethylbenzyl)isocyanurate 3,5-Di-tert.-butyl-4hydroxybenzyl-phosphonic acid-dioctadecylester 3,5-Di-tert.-butyl-4hydroxybenzyl-phosphonic acid-monoethylester Calcium-salt 6. Acylaminophenols 4-Hydroxy-lauric acid anilide 4-Hydroxy-stearic acid anilide 2,4-Bis-octylmercapto-6-(3,5-di-tert.-butyl-4-hydroxyanilino)striazine N-(3,5-di-tert.-butyl-4-hydroxyphenyl)-carbamic acid octyl ester 7. Esters of 4-(3,5-Di-tert.-butyl-4-hydroxyphenol)-propionic acid with mono- or polyhydric Methanol Octadecanol alcohols eg with Diethyleneglycol Triethyleneglycol 1,6-Hexandiol Pentaerythritol Neopentylglycol Tris-hydroxyethyl-isocyanurate Thiodiethyleneglycol Di-hydroxyethyl-oxalic acid diamid 8. Esters of I 6-(5-tert.-butyl-4-hydroxy-3-methylphenyl)propionic acid with mono- or polyhydric alcohols eg with Methanol Octadecanol 1 6-Hexand iol Diethyleneglycol Triethyleneglycol Pentaerythritol Neopenty1glycol Tris-hydroxyethyl-isocyanurate Thiodiethyleneglycol Di-hydroxyethyl-oxalic acid diamide 9. Amides of 13-(3,5-Di-tert.-butyl-4-hydroxyphenyl)-propioni acid eg N, NI-Di-(3,5-di-tert.-butyl-4-hydroxyphenylpropionyl)hexamethylene-diamine NFNI-Di-(3,5-di-tert.-butyl-4-hydroxyphenylpropionyl)trimethylene-diamine N,NI-Di-(3,5-di-tert.-butyl-4-hydroxyphenylpropionyl)-hydrazine Examples of amine antioxidants: N,NI-Di-isopropyl-p-phenylenediamine N,NI-Di-sec.butyl-p-phenylenediamine N.NI-Bis(1,4-dimethyl-pentyl)-p-phenylenediamine NtNI-Bis(l-ethyl-3-methyl-pentyl)-p-phenylenediamine N,NI-Bis(l-methylheptyl)-p-phenylenediamine NiNI-Bis(l-methyl-heptyl)-p-phenylenediamine N, NI-Dicyclohexyl-p-phenylenediamine N,NI-Diphenyl-p-phenylenediamine N,NIDi-(naphthyl-2-)-p-phenylenediamine N-Isopropyl-NI-phenyl-pphenylenediamine N-(1p3-dimethyl-butyl)-NI-phenyl-p-phenylenediamine N-(1Methyl-heptyl)-NI-phenyl-p-phenylenediamine N-Cyclohexyl-NI-phenyl-pphenylenediamine 4-(p-Toluene-sulfonamido)-diphenylamine N,NI-dimethyl-N, NI-di-sec.-butyl-p-phenylenediamine Diphenylamine 4-Isopropoxydiphenylamine 1 G N-Phenyl-l-naphthylamine N-Phenyl-2-naphthylamine octylated Diphenylamine octylated N-phenyl- (or) naphthylamine 4-n-Butylaminophenol 4-Butyrylamino-phenol 4-Nonanoylamino-phenol 4-Isodecanoylamino-phenol 4- Octadecanoylamino-phenol Di-(4-methoxy-phenyl)-amine 2,6-Di-tert.-butyl-4dimethylamino-methyl-phenol 2,41-diamino-diphenylmethane 4,41-Diaminodiphenylmethane N,N,NI,NI-Tetramethyl-4,41-diamino-diphenylmethane 1,2-Di(phenylamino)-ethane 1,2-Di-[(2-methyl-phenyl)-amino]-ethane 1,3-Di(phenylamino)-propane (o-tolyl)-biguanide Di-[4-(1',,3'-dimethyl-butyl)phenyllamine Examples of further metal passivators are:

for copper eg Benzotriazole, tolutriazole and derivatives thereof, tetrahydrobenzotriazole,2-mercaptobenzthiazole, 2,5-dimercapto thiadiazole, salicylidene-propylenediamine and salts of sal icyl am inog uanid ine. Examples of rust inhibitors are:

a) Organic acids, their esters, metal salts and anhydrides eg N-oleoylsarcosine, sorbitan-mono-oleate, lead-naphthenate, dodecenyl-succinic acid (and its partial esters and amides), 4-nonyl-phenoxy-acetic acid.

1 b) nitrogen-containing compounds eg I. Primary, secondary or tertiary aliphatic or cycloaliphatic amines and amine-salts of organic and inorganic acids eg oil-soluble alkylammonium carboxylates II. Heterocyclic compounds eg substituted imidazolines and oxalines C) Phosphorus-containing compounds eg Amine salts of phosphonic acid partial esters, zinc dialkyldithio phosphates d) Sulfur-containing compounds eg Barium-dinonylnaphthalene-n-sulfonates, calcium petroleum sulfonates Examples of viscosity-index improvers are eg Polymethacrylatest vinylpyrrolidone/methacrylate-copolymers, polybutenes, olefin-copolymers styrene/acrylate-copolymers.

Examples of pour-point depressants are eg Polymethacrylates, or alkylated naphthalene derivatives Examples of dispersants/surfactants are eg Polybutenylsuccinic acid-amides, polybutenylphosphonic acid derivatives, basic magnesium-, calcium-, and bariumsulfonates and -phenolates.

Examples of anti-wear additives are eq Sulfur- and/or phosphorusand/or-halogen-containing compounds eg sulfurised vegetable oils, zinc dialkyldithiophosphates, tritolyl phosphate, chlorinated paraffins, alkyland aryldisulfides.

In the treatment of substrates which are completely aqueous, such as cooling water systems, air-conditioning system, steam-generating systems, sea-water evaporator systemsr hydrostatic cookers, and closed circuit heating or refrigerant systems, further corrosion inhibitors may be used such as, for 1 example, water soluble zinc salts; phosphates; polyphosphates; X_ phosphonic acids and their salts, for example, hydroxy ethylidene diphosphonic acidr nitrilotris methylene phosphonic acid and methylamino dimethylene phosphonocarboxylic acids and their salts, for example, those described in German Offenlegungsschrift 2632774, hydroxyphosphonoacetic acid, 2-phosphonobutane-1,2,4- tricarboxylic acid and those disclosed in GB 1572406; nitrates, for example sodium nitrate; nitrites eg sodium nitrite; molybdates eg sodium molybdate; tungstates; silicates eg sodium silicate; benzotriazole, bis- benzotriazole or copper deactivating benzotriazole or tolutriazole derivatives or their Mannich base derivatives; N-acyl sarcosines; N- acylimino diacetic acids; ethanolamines; fatty amines; and polycarboxylic acids, for example, polymaleic acid and polyacrylic acid, as well as their respective alkali metal salts, copolymers of maleic anhydride, eg copolymers of maleic anhydride and sulfonated styrene, copolymers of acrylic acid eg copolymers of acrylic acid and hydroxyalkylated acrylic acid, and substituted derivatives of polymaleic and polyacrylic acids and their copolymers. Moreover, in such completely aqueous systemst the triazole copper corrosion inhibitor used according to the invention may be used in conjunction with dispersing and/or threshold agents eg polymerised acrylic acid (or its salts), phosphino-polycarboxylic acids (as described and claimed in British Patent 1458235), the cotelomeric compounds described in European Patent Application No. 0150706, hydrolysed polyacrylonitrile, polymerised methacrylic acid and its salts, polyacrylamide and co-polymers thereof from acrylic and methacrylic acids, lignin sulphonic acid and its salts, tannin, naphthalene sulphonic acid/formaldehyde condensation products, starch and its derivatives, cellulose, 1 - 17 acrylic acid/lower alkyl hydroxyacrylate copolymers eg those described in US Patent Specification No. 4029577, styrene/maleic anhydride copolymers and sulfonated styrene homopolymers eg those described in US Patent Specification No. 4374733 and combinations thereof. Specific threshold agents, such as for example, 2-phosphonobutane-1,2,4- tri-carboxylic acid, acetodiphosphonic acid, hydrolysed polymaleic anhydride and its salts, alkyl phosphonic acid, hydroxyphosphonoacetic acid 1-aminoalkyl-1, 1-diphosphonic acids and their salts, and alkali metal poly-phosphates, may also be used.

Precipitating agents such as alkali metal orthophosphates, carbonates; oxygen scavengers such as alkali metal sulphites and hydrazines; sequestering agents such as nitrilotriacetic acid and its salts; antifoaming agents such as silicones eg polydimethylsiloxanes, distearylsebacamides, distearyl adipamide and related products derived from ethylene oxide and/or propylene oxide condensations, in addition to fatty alcoholst such as capryl alcohols and their ethylene oxide condensates; and biocides eg amines, quaternary ammonium compounds, chlorophenols, sulphur-containing compounds such as sulphones, methylene bis thiocyanates and carbamates, isothiazolones, brominated propionamides, triazines, phosphonium compoundst chlorine and chlorine-release agents and organometallic compounds such as tributyl tin oxide# may be used.

The compounds of formulae A and B combine excellent copper deactivation properties with good solubility in aqueous- and oil-based substrates.

The following Examples further illustrate the present invention. All parts and percentages given therein are by weight.

- 18 Examples 1 to 11 A 0.05% solution of an equimolar mxture of components of formulae A and B is produced in 75:25 water:ethylene glycol mixture, in which the water contains 0.132 gl-1 M9S04.7H20 and 0.68 glCaC12.6H20 (water as used in DIN 51360 test). The pH of the solution is adjusted to 8.5 with sodium hydroxide.

A piece of copper foil (20 x 50 x 0.1 mm) is cleaned by rubbing with cotton wool soaked with water and powdered pumice, dried and weighed. It is then fully immersed in 50 ml of the solution so prepared in a 60 ml bottle fitted with a screw cap. The bottle is then placed for 24 hours in an oven maintained at 700C. At the end of this time, the strip is removed, washed and dried and its colour is recorded (using the ASTM D130 colour ranking). It is then immersed for 15 seconds in 5N hydrochloric acid at 2CC, washed, dried and reweighed.

The results are summarised in Table I:

11 Compound of Formula A R1 Example

1 2 1 1 1 1 1 1 1 3 1 1 4 1 1 1 1 6 1 1 7 1 1 8 1 1 9 I(C112)3CHO 1 1 1 11 1 1 1 Compound of Formula B R2 CONTROL 1 2-HO.C6H4 12-HO.C6H4 12-HS. C6H4 1 12--M.C6H4 1 12-CO2H.C6H4 1 12-HO.C6H4 1 12-HS-C6H4 1 12-.NH2.C6H4 1 12-CO2H.C6H4 1 12-CO2H.C6H4 1 1 1 1 1 14-CO2H.C6S4 4-SO3H.C6H4 1 % 1 Test Results 1 linhibitioniMetal Appearancel and Rat ing 0 41.9 67.7 83.9 71.0 69.4 95.2 64.5 1 100 95.2 82.2 71.0 1 4D 1 1 1 1Heavy green film 1Heavy brown film] 1 11B 11B 11A/1B 11A/1B 12C 11A 1Heavy brown filmi 13A. 1 1 1 1Black and orangel lareas 1 1 1

Claims

( cl Claims - 20 A method of inhibiting the corrosion of copper or of a

metal containing copper, comprising contacting the surface of the copper, or copper containing alloy with a corrosion-inhibiting amount of a mixture of a compound having the formula A:

R1-C=0 1 H A wherein R1 is Cl-C19 straight- or branched chain alkyl, C5-C12 - cycloalkyl, C7-C13 aralkyl, optionally substituted C61 C10 or C14 aryl', a monocyclic heterocyclic residue having up to 5 ring carbon atoms or a residue of formula I:

-(CH2)n-CHO I where n=1-6:

and a compound having the formula B R2-NH2 B where R2 is Cl-C19 straight or branched chain alkyl, C5-C12 cycloalkyl, C7-C13 aralkyl, optionally, substituted C6j, C10 or C14 aryl, a monocyclic heterocyclic residue having up to 5 ring carbon atoms or a residue of the formula II:

-(CH2)MNH2 II where m=1-6. 2. A method as claimed in claim 1 in which the compound of formula A is one of the formula A( i) CX -11 CH 0 A(i) where X is hydrogen, hydroxyl, thiol or a group CR3 where R3 is H 0 hydrogen or hydroxyl.

1 (I - 21 3. A method as claimed in claim 1 in which the compound of formula A is one of the formula A(ii) OHC(CH2)nCHO A(ii) where n is 1 to 6.

4. A method as claimed in any preceding claim in which the compound of formula B is one of formula B(i) Y c-,, NH2 B( i) where Y is hydrogen, amino, hydroxyl, thiol, carboxyl or sulphoxyl. 5. A method as claimed in any preceding claim in which the mixture contains A and B in a molar ratio of from 3:1 to 1:3. 6. A method as claimed in any preceding claim in which the mixture coptains equimolar amounts of the compounds A and B. 7. A composition comprising a substrate in contact with copper, or a metal containing copper and a copper corrosion- inhibiting amount of a composition of compounds of formulae A and B as defined. 8. A composition as claimed in claim 7 which contains from 0. 001% to 5% by weight, based on the total weight of the substrate, of the composition of compounds of formulae A and B. 9. A composition as claimed in claim 8 which contains 0.01% to 1% of said composition of compounds of formulae A and B. 10. A composition as claimed in claim 9 which contains equimolar amounts of the compounds of formulae A and B. 11. A composition as claimed in any of claims 7 to 10 in which the substrate is a lubricant, a hydraulic fluid, an oil-in-water or water-in-oil system, a metal- working fluid, an engine coolant, a transformer or switch oil, an industrial cooling water, an i 22 aqueous air-conditioning system, a steam generating system, a seawater evaporator system, a hydrostatic cooker or an aqueous closed circuit heating or refrigerant system. 12. A composition as claimed in claim 11 which is oil-based and also contains an antioxidant, metal deactivator corrosion or rust inhibitor, viscosity index improver, pour- point depressantr dispersant, surfactant and/or anti-wear additive. 13. A composition as claimed in claim 11 which is aqueous based and also contains an antioxidant, corrosion or rust inhibitor, metal deactivator, extreme-pressure or anti-wear additive, complexing agent, precipitation inhibitor, biocide, buffering agent and/or anti-foam agent. 14. A method as claimed in claim 1 substantially as hereinbefore described with reference to any one of the foregoing Examples.

Published 1988 at The Patent Office, State House, 66!71 High Holborn, London WCIR 4TP. nnther copies may be obtained from The Patent Office, Sales Branch, St Mary Cray, Orpington, Kent BRS 3PM. Printed by Multiplex techniques ltd. St Mary Cray, Kent. Con. 1/87.