In this paper, the goal is to compute the remaining safety and security factors after apparition of corrosion crater in a gas pipe using probabilistic approaches. For these purposes, we propose to use the failure assessment diagram SINTAP level I coupled with Monte Carlo, FORM or SORM methods.Application is made for a pipe of diameter 219,1mm and thickness 6.1mm submitted to internal pressure of70 bars. Corrosion crater is assumed to be a crack like defect of depth equal to half thickness and crack aspect ratio.