The adhesion and micro-structure of the primary scale formed in LNG combustion gas on steels containing Si, up to 3.0mass%, have been studied using a hot-compression test at 1273K, Raman spectroscopy, and X-Ray absorption fine structure analysis (XAFS). The Fe(2)SiO(4) at the scale/steel interface is increased as the Si content increases, suppressing the diffusion of Fe ions from the steel and forming dense and highly-adhesive subscale, when oxidized below the temperature at which the Fe(2)SiO(4) melts. The behavior of the secondary scale growth in air up to 1173K on these has been studied using in-situ XRD. It is apparent that the formation behavior of Fe(2)SiO(4) FeO and Fe(2)O(3) is influenced by the Si content.