A method of inhibiting corrosion of metal which will be in contact with aqueous, and possibly acidic, solution comprises contacting the metal with a corrosion inhibiting composition containing more than 30% by weight of one or more organic corrosion inhibiting constituents which are water-insoluble hydrophobic material, and a corrosion inhibitor which contains one or more polymerisable groups containing double or triple bonded carbon, before contacting the metal with the aqueous solution. The method may be used to protect coiled tubing used for matrix acidizing of an oil well by propelling a slug of the corrosion inhibiting composition along the coiled tubing before pumping acid through the tubing.