Post-test examination on the slider surface was conducted using optical (OM) and scanning electron microscopes (SEM). OM images of the slider (at time 80 min) shown in Fig. 5 are illustrated in Fig. 8. Faint yellow and blue colours appeared in the image, corresponding to Regions I and II, which are shown in Fig. 8(a). For comparison, the original surface before the test is shown in Fig. 8(b). The slider surface was covered by compact grains of adsorption film. The film in Region II appeared thick and rough, and its blue colour was possibly caused by the Fe ions (Fe+2 and Fe+3) and the electrochemical corrosion of the surface. However, the film was thin in Region I with the polish scratches on the original surface still noticeable. Thus, no corrosion occurred in Region I, but only protein adsorption.