Photochemical cleaning processes of atmospherically contaminated chromium surfaces have been examined by contact angles of water and by time-of-flight secondary ion mass spectroscopy. Exposure of the contaminated surfaces, where contact angles are uniform, to vacuum-ultraviolet radiation results in characteristic distribution of contact angles before all the portions of the plate surface become hydrophilic. The unclean region which has larger contact angle as compared to the averaged value on the plate shows larger intensity of carbon-containing fragments in the spectrum. In order to explain the apparent discrepancy in these results, a model is proposed in which alternate lateral and normal growth of atmospheric clusters occurs on the chromium surface.