Deformation behavior of hot dip galvanized coatings in complex sheet metal forming
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The hot dipped galvanized coatings of flexible tubes with variable corrosion resistances were examined by x-ray diffraction and scanning electron microscopy (SEM). Accelerated corrosion was related to wide cracks formed during roll forming of coatings with coarse spangle sizes and preferred orientation of Zn basal planes parallel to the coating surface. Coarse spangled coatings with reduced preferred orientation of basal planes parallel to sheet surfaces formed only thin cracks and accommodated forming strain primarily by plastic flow. Coatings with fine spangle sizes and preferred parallel basal plane orientations developed networks of fine cracks during forming. The zinc coatings with fine cracks did not expose sufficient steel to cause accelerated galvanic corrosion.
KeywordsBasal Plane Zinc Coating Fine Crack Material Shaping Technology Galvanize Coating
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