Corrosion experiments were conducted on three high-lead and two zinc- base solders in commercial antifreeze coolant solutions, in a rust inhibitor solution, and in corrosive water. The experiments were made to compare the corrosion resistance of presently used soldering systems with that of new systems that can be used for assembling automotive radiators. The high-lead solders, 70pb-30sn, 95pb-5sn, and 95pb-3.8Sn-1.2Ag, are similar to those used to make automobile radiators. The zinc-base solders (95zn-5al and 89zn-7al-4cu) were developed for possible use in automobile radiators. Glassware corrosion tests were conducted on each of the soldering alloys for periods of 336 hours at temperatures of 165 deg and 200 deg f. A limited number of in-service tests were performed by introducing the sample bundles into the cooling system of two automobiles for 10,000- mile tests. Results are presented as the corrosion weight loss in milligrams for each specimen of (1) bulk solder, (2) solder coated copper, and (3) solder coated brass. Corrosion resistance of the soldering alloys and of the solder-coated copper and brass provied to be more dependent on coolant solution type and temperature than on solder alloy composition, whether high-lead or zinc-base type solders. Increased corrosion occurred for both soldering systems in corrosive water; however, the amount of increase was much greater for the zinc-base system. With the exception of the zinc-base bulk solders, the rust inhibitor solution offered little protection to the solder systems tested.