Provided is a coating agent capable of bringing a desired amount of hydrogen into contact with a coated surface without deviation for a predetermined time. The coating agent (100) comprises a first agent (10) which is a powder containing a hydrogen generating material capable of generating hydrogen upon contact with water and a second agent (10) which is mixed with the first agent (10) and contains water And a second agent (20) which is a semi-flowable substance (22).所定時間、所望量の水素を塗布面に対し偏りなく接触させることを可能とする塗布剤を提供する。 塗布剤(100)は、水との接触により水素を発生可能な水素発生材を含む粉体物である第一剤(10)と、第一剤(10)と混合して用いられ水分を含む半流動性物(22)である第二剤(20)と、を備える。
