6.6 Cleaners. Use of a non-etch cleaner is preferred, particularly on wrought alloys. If an etch is used, caution must be taken to prevent pitting or intergranular attack. This is particularly important when using an alkaline etch because the aluminum tends to be more soluble than its alloying elements and existing intermetallics, such as copper, which may be further exposed. As a result, alkaline etching should be avoided (particularly when cleaning assembled structures). If an alkaline etch is used, it should always be followed by an acid neutralization step.