core test of 0 05 or more specifically the specimens 1 to 25 exhibited excellent strength after brazing and excellent brazability the specimens 1 to 25 did not show perforation corrosion when subjected to the swaat test for 12 weeks and did not show separation at the joint when subjected to the swaat test for 8 weeks specifically the specimens 1 to 25 exhibited excellent outer side corrosion resistance as shown in table 10 the specimen 26 had a flow coefficient determined by the mini core test of less than 0 05 due to a low si content in the cladding material 1 and a tensile strength of less than 120 mpa due to a low si content in the core material the specimen 27 did not exhibit sufficient corrosion resistance since the alloy components of the cladding material 1 containing zn flowed to another area due to a high si content in the cladding material 1 as a result perforation corrosion occurred when the specimen 27 was subjected to the swaat test for 12 weeks the specimen 28 did not exhibit sufficient corrosion resistance due to a low zn content in the cladding material 1 as a result perforation corrosion occurred when the specimen 28 was subjected to the swaat test for 12 weeks the specimen 28 had a tensile strength of less than 120 mpa due to a low cu content in the core material the.