The　slab　diffusion　model　based　on　semi-infinite　slab　element　is　usually　used　to　estimate　the　time　to　corrosion　initiation　of　RC　(reinforced　concrete)　circular　column　exposed　to　coastal　atmosphere　zone,　which　ignoring　the　effect　of　the　circular　across-section.　The　diffusion　model　considering　the　diffusion　coefficient　as　time-dependent　variable　and　the　effect　of　circular　across-section　shape,　the　influence　of　the　shape　of　circular　RC　column　exposed　at　coastal　atmospheric　zone　on　the　corrosion　initiation　time　is　analyzed.　The　results　show　that　with　the　coastline　increasing　and　the　radius　decreasing　the　overestimation　of　the　corrosion　initiation　time　by　using　the　slab　diffusion　model　is　the　more　obvious.　A　model　for　calculating　the　bearing　capacity　of　corroded　reinforced　concrete　columns　is　presented,　the　effect　of　the　radius　value　on　evaluating　the　degradation　rate　of　bearing　capacity　of　the　column　at　coastal　atmosphere　zone　under　different　service　periods　is　further　discussed.　The　research　results　show　that　the　increase　of　radius　result　in　the　reduction　of　the　influence　of　corrosion　on　bearing　capacity.　In　the　scenario　of　the　RC　column　located　at　heavy　salt　fog　zone,　the　slab　diffusion　model　can　be　directly　used　to　evaluate　the　corrosion　time.　However,　in　order　to　control　the　degradation　rate　difference　value　caused　by　using　slab　diffusion　model　within　5%,　the　effect　of　shape　on　corrosion　initiation　time　should　be　considered　when　this　column　is　exposed　to　the　light　salt　fog　zone　and　the　radius　is　less　60cm.　And　the　residual　bearing　capacity　of　RC　circular　column　with　different　service　periods　is　further　evaluated.　©　2020,　Editorial　Department　of　JCEE.　All　right　reserved.