In this paper, post‐treatments, including reflowing treatment, passivation treatment, and ultrasonic treatment for tinplates with different coating mass, are discussed, and surface characteristics brought by the post‐treatments have also been investigated by grazing incidence X‐ray diffraction and X‐ray photoelectron spectroscopy. Grazing incidence X‐ray diffraction results show the amount of highest iron and FeSn2 and lowest tin on tinplate with a coating mass of 1.1 g ⋅ m−2, indicating the poor surface coverage of steel substrate. The amount of lowest iron and tin‐iron alloy and highest tin on tinplate with a coating mass of 11.2 g ⋅ m−2 indicates the best surface coverage of tinplate among the four test samples. X‐ray photoelectron spectroscopy depth analysis shows that the sample with coating mass of 1.1 g ⋅ m−2 has a higher amount of iron atomic concentration, which decreases sharply as the coating mass increases, indicating the poor surface coverage by lower coating mass.