Metal Finishing Guide Book

2012-2013

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(a) Cross-section through Delaminated Coating (b) Underside of Delaminated Coating Figure 3. Example of solvent entrapment that has led to a delamination failure. Cross-section (upper image) and underside (lower image) of delaminated sample are shown at the same magnification. and to everyone���s horror the entire system lifted from the steel substrate. The coating delaminated like a sheet. Young Joseph was horrified���the paint had been supplied by his employer! One could clearly see the clean, un-corroded, abrasive blasted substrate shining like new under the coating system. Moreover, one could still smell solvents on the backside of the delaminated coating. Luckily, the customer was neither surprised nor upset. He had been present six years earlier when the railcar was first painted and he remembered the sequence: 1. 2. 3. 4. Steel abrasive blast cleaned with steel shot Corrosion-resistant epoxy primer applied Two coats of epoxy sanding primer applied Primers sanded down using 240 and 320 grit paper until a completely smooth surface was achieved 5. Epoxy filler coat applied 6. Two coats of two-component aliphatic polyurethane applied 7. During inspection all dents and minor coating defects were circled using chalk 578

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