Mechanistic aspects of electrochemical corrosion of aluminum alloy in ethylene glycol–water solution

2009

J Appl Electrochem

The cathodic reaction kinetics and anodic behavior of Al alloy 3003 in aerated ethylene glycol-water solution, under well-controlled hydrodynamic conditions, were investigated by various measurements using a rotating disk electrode (RDE). The transport and electrochemical parameters for cathodic oxygen reduction were fitted and determined. The results demonstrate that the cathodic reaction is a purely diffusion-controlled process within a certain potential region. The experimentally fitted value of diffusion coefficient of oxygen is 3.0 9 10 -8 cm 2 s -1 . The dependence of cathodic current on rotation speed was in quantitative agreement with Levich equation. At potentials more positive than the diffusion controlled region, the cathodic process was controlled by both diffusion and electrochemical kinetics. The electrochemical reaction rate constant, k 0 , was determined to be 1.1 9 10 -9 cm s -1 . There is little effect of electrode rotation on anodic behavior of Al alloy during stable pitting. However, fluid hydrodynamics play a significant role in formation of the oxide film and the Al alloy passivity. An enhanced electrode rotation would increase the masstransfer rate of solution, and thus the oxygen diffusion towards the electrode surface for reduction reaction. The generated hydroxide ions are favorable to the formation of Al oxide film on electrode surface.

Section: Cathodic Reaction Kinetics Under Mixed Controlmentioning

confidence: 98%

Cathodic reaction kinetics and its implication on flow-assisted corrosion of aluminum alloy in aqueous ethylene glycol solution

2009

J Appl Electrochem

“…In Cl À -containing solution, Cl À would be involved in the film formation Al 3þ þ CH 2 CH 2 ðOHÞ 2 ! H þ þ AlðOHCH 2 CH 2 OÞ 2þ (6) AlðHOCH 2 CH 2 OÞ 2þ þ Cl À ! AlðHOCH 2 CH 2 OÞCl þ (7)…”

Section: Effect Of CL à On Corrosion Of 3003 Al Alloy In Ethylene Glyunclassified

“…Cheng's group has performed extensive research on pitting corrosion, FAC and E-C of 3003 Al alloy in the simulated automotive coolant, i.e., 50% (v/ v) ethylene glycol þ 50% (v/v) water þ 10 ppm chloride ions (Cl À ) [3][4][5][6][7]. It is demonstrated that the presence of trace amount of Cl À is critical to pitting corrosion of Al alloy [3].…”

Section: Introductionmentioning

confidence: 99%

Effects of coolant chemistry on corrosion of 3003 aluminum alloy in automotive cooling system

2010

Materials & Corrosion

Self Cite

In this work, effects of coolant chemistry, including concentrations of chloride ions and ethylene glycol and addition of various ions, on corrosion of 3003 Al alloy were investigated by electrochemical impedance spectroscopy measurements and scanning electron microscopy characterization. In chloridefree, ethylene glycol-water solution, a layer of Al-alcohol film is proposed to form on the electrode surface. With the increase of ethylene glycol concentration, more Al-alcohol film is formed, resulting in the increase in film resistance and charge-transfer resistance. In the presence of Cl À ions, they would be involved in the film formation, decreasing the stability of the film. In 50% ethylene glycol-water solution, the threshold value of Cl À concentration for pitting initiation is within the range of 100 ppm to 0.01 M. When the ethylene glycol concentration increases to 70%, the threshold Cl À concentration for pitting is from 0.01 to 0.1 M. In 100% ethylene glycol, there is no pitting of 3003 Al alloy even at 0.1 M of Cl À . Even a trace amount of impurity cation could affect significantly the corrosion behavior of 3003 Al alloy in ethylene glycolwater solution. Addition of Zn 2þ is capable of increasing the corrosion resistance of Al alloy electrode, while Cu 2þ ions containing in the solution would enhance corrosion, especially pitting corrosion, of Al alloy. The effect of Mg 2þ on Al alloy corrosion is only slight.

“…It was proposed that the passive film formed on the Al alloy contains primarily Al-alcohol film, which is resistant to the attack by chloride ions (Cl -). In particular, Zhang et al [23] proposed an electrochemical reaction mechanism to illustrate the formation of the Al-alcohol film. They used energy-dispersive X-ray analysis (EDAX) to detect the presence of a significant amount of carbon in the film, which was assumed to be an indicator of the formation of an Al-alcohol film.…”

Section: Introductionmentioning

confidence: 99%

“…Cheng's group [20][21][22][23][24][25] studied systematically the flow-assisted corrosion and erosion-corrosion of 3003 Al alloy in aqueous ethylene glycol solutions. It was proposed that the passive film formed on the Al alloy contains primarily Al-alcohol film, which is resistant to the attack by chloride ions (Cl -).…”

Section: Introductionmentioning

confidence: 99%

Characterization of passivity and pitting corrosion of 3003 aluminum alloy in ethylene glycol–water solutions

2010

J Appl Electrochem

In this work, the passivity and pitting corrosion behavior of 3003 aluminum (Al) alloy in ethylene glycol-water solutions was investigated using various electrochemical measurements, Mott-Schottky analysis and surface analysis techniques. Results demonstrate that the passive film formed on Al alloy contains both Al oxide and Al alcohol, showing an n-type semiconductor in nature. There is an enhanced corrosion resistance of the Al-alcohol film, which is resistant to adsorption of chloride ions. The pitting corrosion of 3003 Al alloy occurs in the solutions containing a low concentration of ethylene glycol only, where the formed film is dominated by Al oxide. Chloride ions attack and replace the oxygen vacancies in the film, resulting in a local detachment of the film from the Al alloy. A galvanic effect exists between Al alloy substrate and the adjacent second phase particles. Pits form when Al alloy substrate is dissolved away and the second phase particles drop off from the substrate.