A device for applying a protective coating to the weld or solder seam of a can body has an application roller (2) serving to apply a coating material inside a region covering the seam at the inside (15) of the can body. The roller periphery has a cross-sectional profile (5) comprising at least one depression (10) in a middle region (9) of a middle portion (6) having a region width of less than 60% of the width of the middle portion (6). The profile (5) further comprises at least one salient point and/or at least two points of inflection in this middle region (9). The device renders it possible to achieve optimum layer thicknesses of the coating over the seam, which are neither too little for the stresses occurring during the long-term storage of corrosive liquids nor too great for the tearing strength stressing of the coating which occurs during the flanging over of the edges of the can body. As a result of the form of the roller, an optimum profile of the coating layer applied results, with the greatest layer thickness immediately above the seam.