Characterization of blisters on powder coated aluminium AA5006 architectural profiles. (September 2019)

• Record Type: Journal Article
• Authors: Zaffaroni, Giorgio Giovanni Battista; Gudla, Visweswara Chakravarthy; Ud Din, Rameez; Ambat, Rajan
• Is Part Of: Engineering failure analysis. Volume 103(2019)
• Page Start: 347
• Page End: 360
• Publication Date: 2019-09
• Subjects: Aluminium -- Intermetallics -- Interface analysis -- Blistering -- Corrosion; System failures (Engineering) -- Periodicals; Fracture mechanics -- Periodicals; Reliability (Engineering) -- Periodicals; Pannes -- Périodiques; Rupture, Mécanique de la -- Périodiques; Fiabilité -- Périodiques; Fracture mechanics; Reliability (Engineering); System failures (Engineering); Periodicals; Electronic journals; 620.112
• DOI: 10.1016/j.engfailanal.2019.04.039
• Languages: English
• ISSNs: 1350-6307

Abstract

Abstract: Investigation of premature blistering and delamination of coated AA5006 window frames using scanning (SEM) and transmission electron microscopy (TEM), glow discharge optical emission spectroscopy, and X-ray photoelectron spectroscopy (XPS) is presented. SEM of the blisters revealed corrosion of Aluminium and accumulation of corrosion products at the interface of coating and metal. TEM and XPS analysis revealed a thin and non-homogenous hexavalent Cr conversion layer. High number density of intermetallics, and surface defects from metal forming process resulted in a defective conversion coating leading to reduced corrosion protection of aluminium in the presence of water and Cl from atmosphere. Highlights: Blistering of coated AA5006 profiles occurred by corrosion product accumulation at metal-coating interface. AA5006 sheet metal had high number of intermetallic particles due to its recycled nature. Cr conversion coating on AA5006 was inhomogeneous due to surface defects and intermetallics on metal. Corrosion was localised at sites with higher concentration of intermetallics. Moisture and Cl- initiated corrosion, which accelerated due to defective conversion layer and high intermetallics density.