A rust inhibitor which ensures the simplicity of application typical for a coating process and can demonstrate excellent characteristics similar to those obtained with a metal spraying method. The rust inhibitor is manufactured by admixing zinc and aluminum as fine powders of inorganic metals, which are manufactured with a stamping mill to have a flaky shape, to a modified silicone resin solution. A silane-type silicone resin is used for the modified silicone resin solution. For example, a mixed solution of an organosilane-type silicone resin and an oligomer-type silane coupling agent and the like is used.