A forming limit curve for the corrosion resistance of coil-coatings based on electrochemical measurements

Abstract

Forming limit curves (FLCs) are useful tools to predict the safe forming limits of metal sheet. However, existing FLCs are limited to bare metal and the increasing use of pre-painted metal sheet (coil-coatings) requires new limits that take into account the corrosion resistance. In this work electrochemical impedance spectroscopy (EIS) was used to characterise the degradation of a coil-coated system in different states of deformation (uniaxial, biaxial and plane strain). The EIS data provided information about the condition of both paint and metal substrate and was used to devise criteria for minimum acceptable protection. A FLC was produced based on those criteria and its predictions were compared with the degradation of a model deep-drawn cup. (C) 2014 Elsevier B.V. All rights reserved.