Methods of using ionic liquids as corrosion inhibitors

A method of inhibiting corrosion of a metallic surface in contact with an acidic or aqueous fluid comprising contacting the acidic or aqueous fluid with a corrosive inhibiting effective amount of an ionic liquid of the formula:

• R1R2R3R4A+X− (II);
• or
• R1R2R3A+R8A+R5R6R7X− (III)
• wherein:
• A in formula (II) is or contains nitrogen or phosphorus or a heterocyclic ring thereof and wherein each A in formula (III) is independently selected from nitrogen or phosphorus or a heterocyclic ring thereof;
• and
• X is an anion selected from the group consisting of halides;
• hydroxyl;
• hydroxy containing nitrogen or sulfur compounds;
• carbonates;
• alkyl carbonates;
• bicarbonates;
• carboxylates;
• hydroxycarboxylates;
• dithiocarbonates;
• trithiocarbonates;
• xanthates, thiocyanates;
• alkoxides;
• anionic urea;
• anionic alkyl substituted phosphines;
• anionic amino fatty acids;
• anionic alkoxylated fatty acids;
• anionic acrylamido-methyl propane sulfonate/acrylic acid copolymers;
• anionic phosphated maleic copolymers;
• anionic homo or copolymers of an oxirane or methyloxirane;
• anionic metal complexes;
• sulfur or silicon containing anions;
• anionic phosphate esters;
• anionic thiophosphate esters;
• anionic phosphonate esters;
• anionic thiophosphonate esters;
• anionic thiols;
• anionic natural products;
• anionic phenols;
• anionic phenol resins;
• anionic polyacrylamides;
• anionic copolymers of alpha olefins and maleic anhydride, esters, amides, imides or derivatives thereof;
• anionic alkyl substituted phosphines;
• and anionic homopolymers, copolymers and terpolymers of one or more acrylates, methacylates and acrylamides, optionally copolymerized with one or more ethylenically unsaturated monomers;
• and mixtures thereof;
• and further wherein R1, R2, R3, R4, R5, R6 and R7 are independently selected from the group consisting of hydrogen;
• benzyl;
• alkylbenzyl, or oxyalkyl;
• a straight or branched alkyl group, an alkylbenzyl group, an arylalkyl group, a straight or branched chain alkenyl group, a hydroxyalkyl group or a hydroxyalkylbenzyl group;
• and a polyoxyalkylene group;
• and R8 is a straight or branched alkylene group, an alkylene oxyalkylene, or an alkylene polyoxyalkylene or a zwitterion;
• and further wherein R groups may be joined to form a heterocyclic nitrogen or phosphorus containing ring.