CORROSION RATE MONITORING WITH COMPUTERIZED SYSTEMS

Some observations concerning the aims of corrosion rate monitoring, th e choice of the electrochemical parameter, the opportunity of optimisi ng the measurement technique and the usefulness of developing specific software for computerised systems are made. The basic concepts for th e evaluation of the mass loss of metals or alloys are introduced and s ome mathematical formulas of the method of successive approximations a re given. A short description of the SOFTCOR-DC-PHTS code is given, wh ich concerns its improvements and the most important points and stress es the significant differences between this program and commercial sof tware and the potentialities of the present method. The experimental a pplications, concerning the behaviours of Armco iron and SA 182 grades F11 and F22 carbon steels in inhibited 5% by weight HCl solutions at 75 degrees C and SA 106 grade B carbon steel in solutions containing 1 00 gl(-1) of EDTA at 100 degrees C and different pH values, have demon strated the existence of a discrepancy between direct and electrochemi cal determinations of the corrosion rate. The value of the electrochem ical determination of the corrosion rate, obtained through potentiosta tic measurements with a polarization time of 1 s, was higher than the mean value of the direct evaluation from weight loss data. The present results show that the electrochemical technique cannot reproduce the true behaviour of a corrosion process. However, the SOFTCOR-DC-PHTS pr ogram is very useful to deal with the problem of monitoring the corros ion rate of metals in acid media and to process experimental data with out the intervention of an operator. Finally, it has been experimental ly demonstrated that the determination of the polarization resistance depends on the technique adopted for performing polarization measureme nts.