Soldering fins to radiator pipes - using aluminium fins pretreated in bath contg. sodium hydroxide, tin cyanide and urea

摘要

Process as in DT 2018615, in which Al fins are pre-treated e.g pickled, and provided with a stearin-contg. protective layer. The radiator pipes are covered with 1 or 2 layers of a low melting alloy and opt. with a stearin-contg. protective layer. In this modification, the fins are pre-treated in an alkaline bath contg. 10-14% NaOH, 4-7% Sn cyanide and 20-30% urea, for 15-30 secs. at 32-60 degrees C. Protective layer is formed by immersion in a bath of C2HCl3 or alcohol contg. 10-30% technical stearin. Protective layer formed on Al surface, allows soldering and acts as oxidn. protective layer, 2-4 mu-thick.