A method using binarized image data is common to calculate the area of iron rust in a digital image system. However, iron rust includes red rust as well as black corrosion products, and it may be inappropriate to use binarized data. Therefore, we tried to evaluate with a 24-bit color image of sRGB. The areas of red rust, black corrosion products, and metal substrate of a small area iron rust image were visually judged, teacher data was created, and evaluation was performed using a support vector machine. As a result, the image was divided into each area, and the area and its ratio could be calculated.

To verify the applicability of glass-fiber reinforced plastics with an unsaturated polyester matrix in manhole environments, degradation characteristics in a weak alkaline aqueous solution were evaluated by conducting a solution immersion test. We were able to clarify that diffusion of alkaline ions is slower than that of water, effect of accelerated deterioration due to alkali remaining on the sample surface, resin fiber interface preferentially deteriorates due to the diffusion of water, and that the decrease in flexural strength is in good agreement with the logarithmic approximation formula.