Preliminary study of the effect of electrolyte dilution on the electrochemical behavior of aluminum in black wattle pyroligneous liquor in MILD ANODIZATION in galvanostatic mode

Aluminum is a metal widely used commercially and usually with surface anodizing treatment. Anodizing is also a consolidated and widespread process, mainly a potentiostatic technique known as Mild Anodization, which uses organic acids as electrolytes with application of low potentials to generate semiconductor oxide layers. On the other hand, the pyroligneous liquor, which is a by-product of the production of charcoal, arising from the condensation of smoke from pyrolysis ovens as a process for controlling atmospheric pollution, is little known in technological means, being used primarily for agricultural purposes and has mainly organic acids in its composition, such as acetic acid, tar and ketones. On the other hand, anodizing processes are normally carried out in electrolytes that require expensive effluent treatment and controlled disposal. Thus, the aim of this study is to evaluate the behavior of pyroligneous liquor as an anodizing electrolyte for 6061 aluminum at different concentrations. Therefore, process parameters (current density, temperature, time) and three levels of electrolyte concentration were defined - 10%, 25% and 50% v/v. Comparatively, the same process parameters were used for the acetic acid electrolyte (at concentrations of 0.4%, 1% and 2% v/v). The surfaces after electrochemical treatment were evaluated for their morphology, through scanning electron microscopy, and for wettability, by the sessile drop method. It was verified that aluminum was anodized in pyroligneous liquor, while in acetic acid there was surface electropolishing. In the case of the pyroligneous liquor, the results showed that, under the proposed anodizing conditions, the process performance was better at the concentration of 10% v/v.