Progress in Organic Coatings 46 (2003) 161–162

Summary of Presentations and Discussionsof Jurata Workshop

Douglas MillsUniversity College Northampton, UK

Regarding the technical program, the first lecture was byGordon Bierwagen from North Dakota State University andwas entitled “Embedded electrodes for in situ EIS and ENMmeasurements.” The purpose of this work was to try to fol-low the conductivity/protection ability of the coating whenin a ProhesionTM cabinet with the aim eventually of usingsimilar methods to monitor in situ coatings on ships and air-craft. ENM was shown to be more successful than EIS inthis application. Particularly the cycling of the ProhesionTM

chamber (hot/cold & wet/dry) was easily followed from theRn measurements.

Jeorg Vogelsang from Sika Chemie described enhancedsurface roughness due to UV degradation – an unknownsource of EIS artifacts. The conclusion from this work wasthat when, in order to carry out electrochemical measure-ments, a cell is attached by clamping to the surface, careis needed to ensure that no leakage paths were present. Ifpresent these lead to the reading being artificially low and itwas particularly likely to be the case if the surface had beenroughened up e.g. by exposure to UV.

The next paper was an investigation into the mechanismof protection of pigmented alkyd coatings using conductivitymeasurements presented by Douglas Mills from UniversityCollege Northampton. This drew together work conductedin USA on a couple of standard alkyd coatings formulatedfor Navy use with more recent work on alkyd coatings for-mulated for industrial use conducted in UK. Inhibition ex-periments were combined with DC resistance measurementson detached films and together with the Electrochemicalnoise methods applied to attached films helped build up apicture of the mechanism by which these coatings operate.

Lorenzo Fedrizzi of Univ. of Rome “La Spienza”described the use of electrochemical techniques to studypainting cycles for garden furniture. Although all methodsof application were similar for the simple shapes, there wasa difference when it came to the performance of complexshapes in e.g. the hot salt fog test. A cationic electrodepo-

E-mail address: DOUGLAS.MILLS@northampton.ac.UK (D. Mills).

sition primer greatly increased effectiveness and galvanizedsteel was much better than ungalvanized (although the EISmeasurements did not really pick the latter observation up).

EIS was also used by the team from University of Vigoin Northern Spain. Carmen Perez presented a paper us-ing that technique to look at the influence of galvanizedroughness on the behavior of coated weathered galvanizedsteel -. When introduced into a Weathering Cycle Chamberboth roughness and the 10 Hz resistance increased by aboutan order of magnitude with exposure time which was aninteresting observation suggesting that, other things beingequal, it might be possible to measure surface roughnesswith impedance (or even DC measurements).

There were two more papers on the first day. The firstwas by Sebastian Duval et al from Institute Francais duPetrole who discussed some pitfalls in EIS interpretationon organic coatings due to polymer relaxation. This talkemphasized that caution should be exercised in using theBrasher-Kingsbury equation for measuring water uptake(and also the break point frequency method for determiningdelamination promulgated by Huruyama) when the mea-surement is being made above the Tg. The work suggestedthere was a sudden jump in the water uptake about the Tg.

Finally on the first day Stephan Krakowski presented prac-tical talk on the application of electrochemical impedancespectroscopy for evaluation of rubber linings in FGD units.These have very high impedance in general and althoughsmall changes have been difficult to pick up in a plant sit-uation, nonetheless simulation in lab conditions had beenvery successful in relating EIS parameters to the protectionafforded.

The meeting reconvened at 10.00 on the Wednesday whenA C Bastos who works in Alda Simoes group at the Tech-nical University of Lisbon IST described the effect of strainon the protective properties of organic coatings. This was asubject of study ofinter alia Martin Kendig in work doneat Rockwell International in the mid 1980’s. There is nodoubt that cracking is an important failure mode of coatingswhich is sometimes difficult to simulate in the laboratory.

0300-9440/03/$ – see front matter © 2003 Published by Elsevier Science B.V.doi:10.1016/S0300-9440(03)00053-5

162 D. Mills / Progress in Organic Coatings 46 (2003) 161–162

This paper looked at pre-painted metal sheet samples de-formed by uniaxial traction to various amounts from zero to29% strain using impedance measurements. Within 30 daysthe film resistance fell by up to four orders of magnitudeand the double layer capacitance rose by a similar amount.

Antonio Castela who also works in Prof. Simoes groupat the same establishment (IST) described a linear modelfor the impedance evaluation of water absorption in organiccoatings. This had echoes of the earlier talk by Duval. Thispapar proposed a new capacitance model which took intoaccount in linear combination the polymeric phase, the waterand the air in the coating. This gave a better result than thatobtained using the standard Brasher-Kingsbury equation butit was still some way from agreeing with the gravimetricdata.

The final three talks all came from the Technical Univer-sity of Gdansk. The first of these was by Jacek Bordzilowskidescribing Impedance measurements of coating propertieson bridge structures. This was a most interesting paperbecause experiments in the laboratory were compared withmeasurements made on site with cells glued on to both hori-zontal and vertical surfaces of a large modern bridge. Areasbetween 19 and 79 cm were exposed to 3%NaCl for up to24 h with measuring voltages of between 100 and 500 mV.Results were high but measurable. This is an on-goingprogram and the aim will be to monitor intermittently fieldresults.

Next, J. Orlikowski described Impedance measurementsof conductive coatings, work performed under the supervi-sion of K. Darowicki. The conductive coatings were appliedto concrete as anodes in a CP system to protect the under-lying rebar. The typical coating was a graphite containingepoxy at 300 mm and the results showed that 40–45%graphite was the optimum loading.

Finally there was a talk on the effect of environmentaltemperature variations on the protective properties of or-ganic coatings given by Andreas Miszczyk. He stressedion movement quoting Ngyen, Hilbart and Pommesteinin J Coat Tech 68 (#855) (1995) 45 “The degradation oforganic coatings on steel occurs as a result of transport ofions through conductive pathways”. He had gathered muchmeteorological data and pointed out that there is a variationeach day typically from 10–40◦C. He has been simulatingthis in the laboratory and was undoubtedly showing some

effect. In the discussion it was pointed out that the rateof thermal shock was likely to be an important factor. Ingeneral it was more damped (i.e. slower) in the externalenvironment than in the laboratory It was also pointed outthat pigmentation e.g. with aluminum flake in industrialmaintenance coatings could reduce the effect.

This set of a dozen papers were interesting to this writer,particularly because a number of them addressed the areasthat were studied in Dr Mayne’s laboratory at Cambridge be-tween 10 and 40 years ago e.g. effect of temperature cycling,changes at Tg of water uptake, epoxy and alkyd coatings andparticularly the measurement and importance of ionic resis-tance. In Mayne’s lab it was the DC resistance method usingelectrometers which was used to measure this, whereas thesedays EIS or ENM are the preferred techniques. Despite thisincreased level of sophistication it seems we do not knowall the answers yet and more experiments are required!

On the final morning there was a discussion session.This mainly talked about the progress since the SchliffkopfWorkshop, particularly the establishment of the workinggroup within EFC WP 14 to look at Standardization of ACImpedance. This had had three meetings and a request hadbeen lodged to form the WP as part of ISO TC 35 SC9(reviewer’s note: a standards meeting was held in Pittsburgin June 2001 at which this WG 29 was approved). Dummycells had been circulated in a round robin test program towhich about a dozen laboratories had contributed. The finalreport on the round-robin testing will be available fromFritz Blekkenhorst later in the year, but so far the exercisehad pointed up to the users the differences between theirequipment and others. Although currently the emphasis is inchecking and calibrating the equipment, this could move onto interpretation which would involve experiments on actualpainted panels. Note there is an American standard prac-tice (ASTM G 106-89 (re-approved 1994) for “Verificationof algorithm and equipment for electrochemical impedancemeasurement” but this is only applicable to systems withan impedance of about 100 ohms! The other matter was aninitiative by Professor Stuyner from Bulgaria regarding us-ing the internet in relation to a European Standard on useof Impedance. This could also involve an internet exchangeof impedance data and the running of courses on impedancespectroscopy. The group agreed to ask Jorg Vogelsang tokeep an eye on progress of this activity.