Electrochemical noise for field corrosion measurement

This report describes the activities carried out by the two partners (UCL and CSM), concerning laboratory electrochemical noise (EN) measurements, field simulation in laboratory, data treatments and the design and construction of an EN corrosion monitoring system for field corrosion measurements. Laboratory, simulation of field and field measurements were carried out in chloride containing solutions and natural see water on the following materials: cold rolled and zinc coated steel; ferritic (AISI 436 type), austenitic (AISI 304 type) and duplex stainless steels (2304 type). Cold rolled and zinc coating steels were tested under uniform corrosion conditions and stainless steels samples were studied under pitting, crevice corrosion conditions and under application of load. For the correct analysis of EN signals it was necessary to remove voltage drift and DC components in time recordings. They can be eliminated with an analytical procedure of data fitting , i. e. with polynomial fitting or using a digital high-pass filter, i. e. Butterworth filter. Both methods were tested in this report and their effect was analysed by means of the attenuation factor, H(f). Butterworth filter was a suitable system for elimination of drift and DC components. Good agreement was found between the results obtained by EN and conventional electrochemical techniques. In several cases EN technique was more sensitivity. An EN corrosion monitoring system for field corrosion measurements has been constructed and employed for field measurements. Field results showed that it is possible to use the EN techniques to identify, in-situ, the corrosion onset and give information about the kind and degree of corrosion process.