Electrochemical noise as a means of monitoring/assessing organic coatings
Add to calOnline
We are pleased to announce our November meeting, which will be held in collaboration with the Aberdeen Branch of the Institute of Corrosion, and delivered by Dr Douglas Mills and Tianyang Lan.
It is generally agreed that the protection afforded by an organic coating system to a metal substrate can be accurately assessed by measuring resistance (normally ionic, being the largest in the circuit). In sea water environments the criteria set by Bacon, Smith and Rugg some seventy-five years ago that a resistance of greater than 1x108 ohms/cm2 was a good coating, 1x106 to 1x108 ohms/cm2 was fair and less that 1x106 ohms/cm2 was poor, is still accepted.
The two main methods of measuring this are Electrochemical Impedance Spectroscopy (EIS) and by Electrochemical Noise Measurement (ENM). The speakers prefer the latter for the relative simplicity of the measurement and its non-intrusive nature. Recently the assessment of protection by ENM has been made easier to carry out by the availability of a purpose-built propriety device (ProCoMeter) designed to make measurements in the field and offering various electode arrangements. Work at the University of Northampton and elsewhere has tested three such arrangements (Bridge, SSS and NOCS) and each gave similar results of resistance for coatings.
Bridge (or beaker) is the standard way of conducting ENM with two nominally separate but identical metal samples and a reference electode. This could be used for coatings. But when it comes to assessment of inhibitors or monitoring of these, it has to be used. Some results obtained using the bridge arrangement in testing a number of inhibitors both green and standard will be discussed for corrosion of steel in hydrchloric acid.
It will also be shown how ENM gave comparable results to the more established Linear Polarisation Resistance (LPR) method. The work with coatings will concentrate on the identified problem that in any arrangement of ENM the results come from two separate areas and the resistance value is an amalgamation, i.e. the two areas could have different resistances. Identifying when this is the case has been addressed by making multiple measurements and looking at other parameters apart from resistance, for example voltage and voltage noise. These results will be shown, and the results discussed.
Extending this technique to trials in the field is the next step.
Dr Douglas Mills did his PhD on anti-corrosive coatings at Cambridge University and has worked on and off in this field ever since. After spells at the BNF Metals Technology Centre and the Nuclear Power Company, in recent times he has worked in academia and, apart from teaching materials, has continued to conduct and supervise reseach in the field of electrochemical methods for application to coatings, particularly studying and developing the electrochemical noise method. Douglas was the Technical Secretary of the Institute of Corrosion for 15 years and is also involved in the development of Standards.
Tainyang Lan studied for his BSc and MSc in General Engineering at the University of Northampton. During his studies he conducted some Electrochemical Noise research projects under the supervision of Dr MIlls. He worked on a research contract at the University of Nottingham in the Department of Environmental Engineering applying ENM and LPR to the testing of green inhibitors. He is now working at the DCVG Company which provides various equipment for detection (using ENM) and prevention (using coatings and CP) of corrosion of pipelines.
The lecture will delivered virtually via Zoom; please register using the following link: https://us06web.zoom.us/webinar/register/WN__mxGyL7xSm2aL0HHa5Ar1w
For more information contact the organising team.
