Weathering steel specimens were exposed for 4 years and a compacted rust layer was formed with a result of lowering down the corrosion rate of the steel. As the mechanical performance of the interface layer can affect the protective ability of rust oxide layer during the service of weathering steel, the bonding strength between oxide layer and substrate steel was evaluated by means of indentation test. A quantitative evaluation of the adhesion is presented by analyzing stress-strain condition near the inter...