The invention relates to a process for reducing the residual hydrogen fluoride gases in a fluorinated plastic tank, in particular in a plastic tank for a motor vehicle, in which firstly the space within the tank is subjected to a fluorination step and then, in at least one gas flushing process, the reaction products of the fluorination step are removed from the plastic tank. In a process in which the undesired reaction product hydrogen fluoride is completely eliminated and which is suitable for efficient large-scale production, after the gas flushing process, a neutralization step is carried out to bind residual fluorination gases on the inner layers of the plastic tank.