Pit Growth of AA 1050 Aluminum Plates Electrograined in Nitric Acid

Abstract

AA 1050 aluminum lithographic plates were ac electrograined in nitric acid electrolyte using a flow cell. Scanning electron microscopy was employed to characterize the surface morphology of the electrograined aluminum plate. An epoxy replica technique was utilized to reveal the internal structures of the etch pits. Cross‐sectional transmission electron microscopy was employed for revealing the detailed morphology of the etch pits and the microstructure of the etch film. Together with the surface property measurements such as Ra , Rmax , peak count, and relative increase factor, a pit nucleation and growth sequence is discussed. Numerous hemispherical pits nucleated and grew on the original aluminum surface upon ac electrograining. One‐dimensional and two‐dimensional coalescence of the individual hemispherical pits led to the formation of crescent‐shaped and convoluted pits, respectively. Secondary stage of pit nucleation and growth occurred dominantly on the walls of the convoluted pits. Formation of convoluted pits on the walls of the existing convoluted pits resulted in a pronounced increase in Ra and Rmax . Meanwhile, a decrease in peak count and relative increase factor was observed for prolonged electrograining. In addition, the microstructure of the etch film was closely related to the morphology of the etch pits. © 2000 The Electrochemical Society. All rights reserved.

Formation of the Layered Etch Films on AA1050 Aluminum Plates Etched in Nitric Acid Using Alternating Currents

“…Compared to the dark-contrast layer, the lightcontrast layer was porous and contained many microvoids. Since similar layered etch films have been observed on the pits formed in nitric acid via the sinusoidal current, 13,15 they must be associated with aluminum etched in nitric acid regardless of the ac waveform. Like the layered etch film formed in nitric acid using the sinusoidal current, 15 EDS spectrum ͑not shown here͒ taken from the darkcontrast layer consisted of aluminum and oxygen signals, suggesting the dark-contrast layer was aluminum hydroxide.…”

“…Since similar layered etch films have been observed on the pits formed in nitric acid via the sinusoidal current, 13,15 they must be associated with aluminum etched in nitric acid regardless of the ac waveform. Like the layered etch film formed in nitric acid using the sinusoidal current, 15 EDS spectrum ͑not shown here͒ taken from the darkcontrast layer consisted of aluminum and oxygen signals, suggesting the dark-contrast layer was aluminum hydroxide. Except aluminum and oxygen, the light-contrast layer mainly consisted of carbon, which is the primary constituent of the M-Bond epoxy used for sandwiching two etched plates together during sample preparation.…”

Etch Film and Pit Structure of AA1050 Aluminum Plates Electrograined in Nitric and Hydrochloric Acids

“…The C and Si originated from the M-Bond epoxy used for sandwiching electrograined aluminum plates for TEM sample preparation, as demonstrated in our previous work. 20 The M-Bond epoxy flowed into the gap between each layer when preparing the TEM sample. Therefore, the etch film was characterized as a layered amorphous structure.…”

“…Microstructural characterization.-The surface morphology of the electrograined aluminum plates was investigated via SEM, and an epoxy replica method was employed to examine the internal structure of the etch pits. 20 Cross-sectional TEM specimens were made from the as-grained aluminum plate via a combination of mechanical grinding and the ion-beam thinning method. 20 Meanwhile, TEM specimens were examined via a JOEL JEL3010 analytical z E-mail: linyang@mail.dyu.edu.tw TEM.…”

“…20 Cross-sectional TEM specimens were made from the as-grained aluminum plate via a combination of mechanical grinding and the ion-beam thinning method. 20 Meanwhile, TEM specimens were examined via a JOEL JEL3010 analytical z E-mail: linyang@mail.dyu.edu.tw TEM. In addition to the detailed microstructure, particularly the pit morphology and etch film structure, energy-dispersive spectroscopy ͑EDS͒ was employed for composition analysis.…”