Bend testing was performed to evaluate resistance to cracking of the pre-treatment during forming. A modified version of the “Standard Test Methods for Mandrel Bend Test of Attached Organic Coatings, ASTM D522M-17 Test Method B” (1) was performed on 102 mm x 152 mm E-Form Plus panels by bending them over a 3/8th inch diameter cylindrical mandrel. The procedure was modified because the test calls for bending fully painted panels over increasingly small diameter cylinders and visually inspecting for paint cracking. Pretreatment D is on the nanoscale coating, so cracking is not visible to naked eye. Instead of bending the samples over increasingly smaller diameter cylinders, the smallest available cylinder diameter was used. Subsequent evaluations including FE-SEM analysis, confocal microscopy, and humidity testing was performed over the bent panels.
Humidity testing at 100% RH and 100 °F resulted in no apparent increase in oxidation (Figure 1).