The susceptibility of vacuum annealed stainless steels to corrosion suggests a surface composition which is depleted in chromium. Direct confirmation of this has been obtained by soft x-ray appearance potential spectroscopy using a multiple sample arrangement in which samples of Cr, Fe, Ni, and 304 stainless steel were analyzed under identical conditions. This provides a reasonable calibration for the determination of surface concentration ratios only if the band structure of the constituents are nearly unaffected by alloying. Experimental evidence that this is approximately so for 304 stainless steel is presented. Using this calibration, the surface composition was determined as a function of isochronal annealing.