Corrosions of pipes have been disregarded as a management object in chemical or petrochemical plants because an outside corrosion phenomenon has a slow deterioration speed. Therefore, there is danger of a large number of pipes that have been used for 30 to 40 years without maintenance. It may cause penetration through pipes due to outside corrosion, in the worst case, a fatal accident will occur. In such a background, proper maintenance work should be carried out in advance. In this research, the case database is made from corrosion rates with environmental factors of design information and installation environment of pipes. A selection support system based on the case databases searches for corrosion points where corrosion is likely to progress. The case databases are successfully evaluated by the degree of diversity and the degree of consistency.