The Chemistry of Brazing Fluxes and Acid Pickling

摘要

Silver brazing is often discussed at various meetings at the Society of Model and Experimental Engineers (SMEE). I give a talk on adhesives, soldering, and brazing to students on our basic training course, and we show Johnson Matthey's video of good brazing practice. We demonstrate brazing the boiler for Tubal Cain's 'Polly' engine to students on our beginners' course, and Keith Hale of CuP alloys gave a nice talk on brazing at a Society meeting. Each time brazing is described, pickling comes up for discussion, often with reference to using sulfuric acid to remove flux residues and oxides. Our recommendation to students on our training courses at SMEE has long been to use nothing more active than dilute citric acid solution, and we disposed of the sulfuric acid in our workshop some years ago, but the subject came up again this year and seems to come up so often that I began to wonder what the authorities on the subject say and why.