Investigating the long term effects of creep with chromate free primers

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Creep has negative conations in many walks of life. It is no different in the field of Coil Coated metal. Creep describes what happens when corrosive materials insidiously force their way between the two halves of the paint metal interface. The process starts from the cut edge of a piece of painted metal advancing inwards at a rate determined by the strength of adhesion, the anticorrosive weaponry lined up against it and of course the strength of the conditions pushing the chemicals forward.Chromate Free Primers for Galvalume suffer badly from edge corrosion. Some people believe that this slows down after a period of time and coatings on substrates such as Galfan and HDG 'catch up' on the extent of creep from the cut edge after a period of time (5 years) but at Beckers we have not seen this. We would like to understand the differences between edge corrosion on galvalume and the other 2 substrates. To this end we would like to apply the electrochemical methodology; Scanning Vibrating Electrode Technique (SVET) to a small selection of primers plus topcoats applied to the above mentioned substrates. Project aims:The aim of the project is to characterise the cut edge corrosion that takes place on Galvalume, Galfan and Hot Dip Galvanised Steel using electro-chemical techniques. The panels will be coated with chromate containing and chromate free primers plus topcoats. A maximum of 2 different anti-corrosive pigments will be tried. Any differences will be investigated and the parameters that impact on the speed of cut edge corrosion will be addressed in an effort to slow down the rate of edge corrosion. Correlations between electrochemical testing, Salt Spray and Exterior exposures will be attempted.