Electrochemical Behavior of Chemical Conversion of Coated Aluminum 1100Al in a Neutral Tartrate Solution

Abstract

1100 Al specimens were anodically oxidized in different concentrations oftartaric acid-tartrate solution (pH=7) in 1, 1.75, 3.25 and 4 wt % at temperatures of30, 37.5, 52.5 and 60 ºC by applying a range of potentials of 30, 37.5, 52.5 and 60V at exposure times of 40, 47.5, 62.5 and 70 min.. These four variables aremanipulated through the experimental work using Box – Wilson experimentaldesign where second order polynomial model was proposed to correlate the studiedvariables with the thickness of anodic film of aluminum alloy (1100) to estimatethe coefficients of the proposed polynomial adopted via statistica software.Optimum conditions for achieving the maximum film thickness are obtained fromoptimizing the above correlation and are found as follows: temp. = 44ºC, acid conc.= 2.8 wt %, voltage = 43.6 V, time = 54.6 min.. Stagnate Solutions of 3, 5, 10 and25 wt % Nacl at 25ºC have been investigated using polarization technique atoptimum conditions for anodizing. The most important feature achieved was thegreat difference in behavior between the anodic polarization curves for bare andanodized aluminum in different concentrations of Nacl solutions. The corrosionrates for anodized specimens are lower than those for unanodized ones. Thepolarization behavior of anodizing specimens shows that the breakdown potentialsare shifted to more noble direction than bare specimens which is more pronouncedin 25 wt % Nacl solution due to anodizing.