Computerised control and data acquisition for corrosion experiments

Abstract

Electrochemical measurement of corrosion involves imposition of electrical perterbation in the form of potential or current on the test specimen and measuring its response. A potentiostat is most frequently used for this purpose. The present paper describes a menu driven user friendly software developed for corrosion analysis by interfacing the potentiostat with PC-AT. The system was developed around a laboratory developed potentiostat and a PC/AT 486.The interface between the two was devel-oped using a PC plug in PCL 208A card with nominal speci-fications : AD 16 ch., DA 2ch, res 12 bits, max. frequency 100 KHz. The DA channels were modified for bipolar output and fine turfing of potential. Corrosion rates are measu-red by (i) linear polarisation, (ii) Tafel analysis and (iii) increasing pulse polarisation. The corrosion rate is calculated using Stern Greary equation with Rp measured from the polarisation data and known tafel slopes. Alterna-tively it is calculated using a nonlinear least square alg-orithm. Besides corrosion measurement the system is also used for other experiments like potentiodynamic polari-sation, pitting, cyclic voltametry, EPR and transients. The specification for the present system are : control potential range ±2V, resolution 0.488 mV, current sensit-ivity 0.1 uA, scan rate 0.26 uVlsec to 20 Vlsec, pulse potential 1.2 mV to 5V, pulse time 250 ms. to 72 mins. Completely arbitrary waveform can be generated and imposed on specimens. The software has facility for preview of potential wafeform, simultaneous display of acquired potential/current data, drawing of lines and tangents, data viewing and editing and calculation of different corrosion and electrochemical parameters.