ALTERATIONS IN THE GALVANIC CURRENT DENSITY AND THE GALVANIC POTENTIAL OF THE COPPER/AISI304 PAIR IN LiBr SOLUTIONS AT DIFFERENT FLOW STEPS USING A ZERO-RESISTANCE AMMETER (ZRA)

摘要

The objective of this work is to determine the effects of flow variations on galvanic current density and galvanic potential at different flow steps using a zero-resistance ammeter (ZRA). The flow steps consist in applying a flow rate for sixty minutes after leaving the system in static regime for one hour; this procedure is repeated during eight hours. The magnitude of the steps is different depending on the flow regime studied, ranging from a Reynolds number of 633 to 5,066. The materials tested consisted of a copper/AISI 304 stainless steel pair in an 850 g/L LiBr solution at 25°C. These materials are commonly used in absorption systems, in which LiBr can cause serious corrosion problems. The results show that, when a flow step is applied, the galvanic current density increases and the galvanic potential decreases. However, with time, this increase in galvanic current density is lower, reaching its lowest value in the last hour of the experiment at a Reynolds number of 5,066. Thus, although the corrosion rate increases as the Reynolds number increases, the protective corrosion products are generated earlier on the copper surface.