Why Do Aluminum Coil Stocks Have White Patches

Manufacturers of large-sized aluminum alloy products would be irritated by the problem of white patches on the surface of aluminum coil stocks, especially anodized ones. Here Haomei would like to have a detailed explanation to this problem. Most of the time it’s normal for white patches to appear on aluminum coil stock surface because a thin dense layer of oxidized film comes into being during the oxidization process and the film takes on the color of white on the surface. In spite of this, it’s really crucial to avoid the appearance of white patches in the manufacturing process, for the brightness and cleanness of aluminum products have a great impact on following surface treatment processes as well.

Generally speaking, aluminum coil stocks have withe patches because the rolls have not been cleaned completely after being anodized. Incomplete washing of the roll surface lead to white patches after the roll gets dry. An effective solution is thorough washing with a hydraulic giant. Operators should avoid damaging the roll surface during washing and have the roll isolated from other products after washing. In this way, the coil stock will get dry naturally. In addition, the concentration of applied washing solution, either acid or alkaline, must be kept under control. Painting also helps to prevent aluminum and oxide from having reactions. In a word, if you want to solve the problem of white patches on aluminum coil stock surface, you should follow strict processes during the whole manufacturing procedure.