In this study the existing degradation model for the coated steel member is reviewed, and a new model is recalculated with the deterioration index, ‘rusting’ and ‘flaking’ only. In the case of durability evaluation with the two indexes only some considerations are suggested by the comparison of the existing and recalculated degradation model.

The correlation between the degradation scores and service life of the coating is derived by tests and inspection for the coated steel member according to each service environment of several facilities. This correlation called to as the deterioration model can be used to determine the performance grade for the durability of coated steel member of facilities under each service environment, for example, atmospheric, fluvial and marine environment.

Indices are selected for the evaluation of deterioration of coated steel, and an evaluation method is proposed for each index. The evaluation methods proposed in this study are then applied on the existing inspection data measured on site, and the correlation between the resulting evaluation scores and service life of the coating is derived statistically. This correlation called to as the deterioration model can be used to determine the performance grade for the durability of coated steel.

This study was conducted for the development of degradation model for the coated steel member in the atmospheric environment. Field inspection data was assessed against the existing evaluation factors which were proposed by the related research process. A correlation between evaluated degradation score and service life of coated steel member was plotted on the graph, and degradation of the coated steel member could be evaluated by quantitative analysis method.