Corrosion behavior of Al&amp;lt;sub&amp;gt;7&amp;lt;/sub&amp;gt;Cu&amp;lt;sub&amp;gt;0.2&amp;lt;/sub&amp;gt;Si&amp;lt;sub&amp;gt;0.2&amp;lt;/sub&amp;gt;Zn&amp;lt;sub&amp;gt;0.2&amp;lt;/sub&amp;gt;Mg&amp;lt;sub&amp;gt;0.1&amp;lt;/sub&amp;gt; complex concentrated alloy, in 3wt% and 5wt% NaCl solution