For the determination of the welding current to be used for the resistance welding of the overlap seam of container bodies, welding with a test body is carried out with a changing strength of welding current which in the test body produces a varying welding of the seam. The current strength varies from welding of this seam with a too high temperature to welding with a too low temperature. Along with this the welding current strength used in the welding is determined so that it is further determined at which point of the seam the welding has been accomplished and with what strength of welding current. By means of a mechanical and/or optical investigation of the welded seam it can then be easily determined where the seam has been correctly welded for the series production of container bodies from the same sheet material as the test bodies. When such a point or such a region of the seam is known the welding current used in the test welding can be taken as the welding current for serial production.