Some observations on the break-through of protective oxide films on iron-chromium alloys

摘要: Abstract The break-through of thin protective films on pure iron-chromium alloys to give thick stratified scales has been studied by metallography and briefly electron-probe microanalysis. During oxidation in air at 1000°C the interference colours produced initially soon disappear layer, consisting a mat small crystals, becomes apparent. This film thickens slowly declining rate may persist places for least 420 min, rarely being more than 1μ thick. A few nodules scale are formed after 5–60 min but these become larger frequent 60–120 min. vary widely shape size apparently random sites surface. Eventually covers whole specimen all layers continue thicken roughly same rate. Extensive internal is often observed behind or never oxide. Scales thicker about 2μ be usefully examined cross-section microanalysis thinner must plan. extremely rich chromium, probably Cr 2 O 3 with quantity Fe , virtually iron oxides form outer layers. mechanism discussed light variation distribution chromium alloy various stages oxidation.