Corrosion is a serious problem that affects several industries and causes significant economic losses. In recent years, the transportation industry has replaced several ferrous parts with aluminum or magnesium alloys to produce lighter vehicles. Due to this, galvanic corrosion has been more frequent in that industry. In this work, a colorimetric sensor for the detection of Al(III) species during galvanic corrosion is presented. The sensor was made of a chromophore immobilized on a gel electrolyte based on NaCl and agar. The sensor developed a red coloration proportional to the Al(III) concentration under the pH interval studied (3.2–4.5). A galvanic couple consisting of an aluminum alloy and carbon steel was used to test the capacity of the sensor to develop the production of Al(III) into the gel electrolyte and over the whole aluminum surface. Through image processing, it was possible to construct 2D Al(III) concentration maps over time using a commercial aluminum alloy (AA7075) and a castable aluminum alloy from a steering rack as a real sample.

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