Surface analysis of thin films and interfaces in commercial aluminium products

Interfaces in commercial aluminium-based products like surface coated sheet and extrusions, laminates and metal matrix composites are of decisive importance to the producer and customer as regards product performance and long term quality. The application of surface-sensitive techniques [x-ray photoelectron spectroscopy (XPS), secondary ion mass spectrometry (SIMS), secondary neutral mass spectrometry (SNMS), x-ray fluorescence spectroscopy (XRF), transmission electron microscopy (TEM)] to study and control the composition and structure of oxide layers and conversion coatings, which become the interface in aluminium-polymer products, is discussed. Quantitative evaluation of surface enrichment processes of alkali and earth alkaline metals during aluminium foil annealing allows the producer to establish quality relevant upper limits for the concentration of these impurity elements. Two further examples are related to solid-liquid interfaces and cover the influence of oxide films on the etchability of high purity aluminium for electrolytic capacitors and the surface composition of aluminium-gallium (AlGa) alloys during alkaline etching with Ga surface enrichment having a large influence on the electrochemical potential of this battery anode material.