INTERNALLY TIN-PLATED COPPER PIPE MANUFACTURING METHOD

A process for manufacturing a copper tube with a tinned inner surface by circulating a substitution-type electroless tin plating solution inside the copper tube. The process is characterized by comprising a first plating step wherein the rate of deposition of a tin film is adjusted so that the total copper ion concentration in the plating solution, immediately after flowing from the copper tube after having been circulated inside the tube divided by the tin (II) ion concentration in this plating solution is 0.8 or less, and a second plating step wherein plating is carried out at a plating solution temperature higher than the plating solution temperature in the first plating step. A plating solution comprising 0.05-0.3 mol/l of Sn ion, 0.5-2.0 mol/l of thiourea, 0.5-2.0 mol/l of sulfuric acid, 0.05-2.0 mol/l of alkyl benzene sulfonic acid, and 0.5-5.0 g/l of a nonionic surface active agent is preferably used. The process ensures manufacture of long coiled tubes with tinned internal surface which are used as water supply tubes, hot water supply tubes, and tubes in heat exchangers. The tin plate film has a uniform thickness and exhibits superior adhesion properties and corrosion resistance.