EVALUATION OF CORROSION RESISTANCE OF MILD STEEL - COPPER BRAZED JOINTS
铜-低碳钢钎焊接头的耐蚀性评价

Copper-zinc,silver-copper and copper-phosphorus brazing alloys are used in the brazing of mild steel pipe to copper pipe,and the corrosion resistance of brazed joints are evaluated using macroscopic observation,metallographic examination,dynamic corrosion test,SEM and EDX analysis.Cracks appear at the interface between steel and braze metal when copper-phosphorus brazing alloy is used,and the joint fails from this place after being corroded.The appearance of the braze metal is fine when copper-zinc brazing alloy is used,but there is localized corrosion in the braze metal and obvious general corrosion in the wall of the copper pipe after being corroded.In contrast with the above-mentioned two brazing alloys,the joint produced by the silver-copper brazing alloy is sound.Its appearance is fine,and its corrosion resistance is also high enough to meet requirements.It is suggested that silver-copper brazing alloy should be used in the brazing of mild steel to copper.