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Electrochemical Impedance Spectroscopy (EIS) and Thermal Wave Imaging (TWI) are complementary techniques which can be used to detect and estimate Impact Induced Corrosion (IIC) at the metal-polymer interface. This paper describes the use of the above techniques to detect Impact Induced Corrosion in a variety of pre-coated and painted sheet steels. It has been possible to show, that IIC is a threshold phenomenon and depends on the type of galvanized coating. Evaluation of IIC, using a high performance indoor accelerated test and preliminary data from the proving grounds are presented in this paper.

An extensive atmospheric corrosion test program to simulate automotive field conditions has been successfully completed. This paper focuses on the corrosion results from the widely exposed AISI set of correlation panels for cosmetic corrosion. Eight factorially designed 12-week tests have been performed in the laboratory, using high performance test equipment, capable of simulating diverse outdoor conditions. The results have been compared with those of outdoor scab exposures and reference panels on vehicles, running in Canada and Sweden. The influences of six corrosive test variables on the response creep-back from scribe on the painted panels are demonstrated, based on a statistic evaluation of the test matrix. All higher settings of the introduced accelerating test variables have each resulted in a decrease in the test correlation with on-vehicle exposures.

An extensive atmospheric corrosion test program to simulate automotive field conditions has been undertaken. The aim of this project is to identify the necessary and sufficient key corrosion variables in appropriate dosage levels in order to design an indoor general purpose accelerated corrosion test. This approach is based on a careful study of outdoor conditions that an automobile typically would encounter along with inputs from current understanding in the area of corrosion and material properties. A 26-3 factorial design was used to implement this test program. Simulating conditions such as humidity, temperature cycling, acid and/or salt depositions, generation of dew and the presence of minute amounts of air pollutants have been achieved by the design and implementation of a high performance climate chamber. A large matrix of painted metal substrates and some bare metal samples along with previously studied AISI samples constitute this study.

An investigation of 14 different precoated sheet steels with an uncoated sheet material as a reference was carried out. The materials used represent a broad spectrum of hot dip, electrogalvanized and prepainted materials. The sheet materials are commercially available and intended both for car and for truck production. The phosphated surfaces were characterized from the point of view of coating weight, shape and size of the crystals formed. Both spray and dip phosphated panels, with the phosphatization made in car production lines, were examined. The painted sheets were examined with a cathodic electrophoretic primer (EC-coat) only and with a full paint system (4 coats). The paint adhesion was shown to be lower for zinc-nickel and for zinc-iron compared with the reference, but for prepainted panels an increase was observed. The rest of the materials did not show any significant difference compared with the reference.