Aluminium corrosion inhibiting primers

The laminates consist of alternate layers aluminium (0.2-0.5 mm thick], which has been anodised and then primed with Cytec-Fiberite s BR-127 corrosion-inhibiting primer, bonded together with fibre-rich, epoxy-based adhesive-prepregs (about 0.125 mm thick]. The reinforcing fibre is usually unidirectional in nature, although woven fabric is occasionally used. Generally two or three sheets of adhesive separate each sheet of aluminium this can be in the 0° direction or laid up in a cross-plied orientation. 

Another type of primer which has already been mentioned are those especially formulated to be applied to chemically treated aluminium alloys in particular, with the main aim of further improving the durability of joints prepared from these pretreated substrates [e.g. 205-209]. They are commonly referred to as corrosion inhibiting primers and are proprietary formulations which typically contain phenolic, epoxy and chromate species. They are used extensively in modern aircraft structures. They will be discussed in greater... 

Item (iv) concerns corrosion inhibition. The reagents most commonly employed are strontium or zinc chromates. As only those particles in direct contact with the steel or aluminium surface are effective inhibitors, it is reasonable to apply them in a suitable binder in as thin a layer as possible. Etch primers, such as are used in paint technology, are unsuitable for use with adhesives and the etching must be carried out as a separate operation as has been discussed in detail above. Where a chromic acid process has been used to prepare the surface, some chromate becomes incorporated therein and the use of a chromate-containing primer seems superfluous. 

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