The boundary lubrication of A1 alloys 6061 (AI-6% Si) and A-390 (Al-18 wt% Si), by a sec-ZDDP (zinc dialkyldithiophosphate) oil blend was examined at 60 andl00~ The wear performance in the ZDDP blend was an improvement on base stock. At 100~ the ZDDP prevented scuffing, though no antiwear films could be detected due to the severe wear. At 60~ all samples showed initial scuffing followed by a more controlled wear given by an embedded antiwear film. P L-edge X-ray near-edge structure (XANES) spectroscopy using synchroton radiation was used to characterize the antiwear and thermally generated deposition films on the A1 alloys. P L-edge XANES results of the antiwear films at 100~ showed the absence of a polyphosphate film. A well-developed polyphosphate film was indicated at 60~ very similar to that formed on steel at 100~ P L-edge XANES results of the thermal deposition films showed the presence of only unchanged sec-ZDDP at 125~ with no polyphosphate present. A polyphosphate film was present at 200~ similar to the antiwear film for A1 alloy at 60~ and steel at 100~