Étude électrochimique du couplage galvanique cuivre/brasures dans les installations d’eau potable

Electrochemical study of the copper/brazing galvanic coupling in drinkable water piping

¹ Lab. de Physicochimie Industrielle, INSA de Lyon, Villeurbanne
² Lab. d’Electrochimie, Université Hassan II, Fac. des Sciences I, Casablanca, Maroc

Abstract

The present work deals with studies by stationary electrochemical methods of coupling cop- per/brazing corrosion behaviour in different conditions: immersion time (5 min to 10 h), soft and hard water (5°F and 30°F), water temperature (18°C to 80°C) and flow velocity (0 to 2 m/s). Three different brazings were studied. According to immersion time at E_corr, the passive film formed at the sample surface depends on the subs tract composition and on the water nature. It is more noble on phosphorous brazing than the one formed on copper. According to the flow velocity, the film formed on the brazing is more resistant than the one formed on copper. According to the temperature at constant flow velocity, the film formed on brazing becomes more resistant with CaCO₃ precipitation where the film formed on copper turns to be less protective, because some of it’s compounds dissolve.

The coupling of copper with phosphorous brazing is unfavourable and leads to a galvanic corrosion especially in hot circulating water. A corrosion-erosion of copper can also be developed at high flow velocity and becomes responsible for major corrosion.