system and method according to the first aspect of the present invention which further comprises an electrochemical step after the acidic removal step for removing an iron containing e g steel casing 2 from a well 1 as in fig2 the casing 2 is fixed in the formation by cement 3 and the interior of the casing 2 forms the well bore additionally as in fig2 the casing 2 which is electrically conducting is connected to the positive pole of a power source 10 also as in fig1 and 2 the system comprises a first fluid line 4 connected to a tank 6 on the surface not shown an electrolyte typically sea water is injected into the well bore via the first fluid line 4 in fig3 the cathode which is connected to the negative pole of the power source is formed by the exterior surface of the first fluid line 4 in this embodiment the exterior surface of the first fluid line 4 is partially electrically conducting and partially insulating thus in the interval 20 where iron containing e g steel casing is to be removed the exterior surface of the first fluid line is electrically conducting whereas in the areas 21 22 where the iron containing casing is to remain the exterior surface of the first fluid line 4 is non electrically conducting e g coated with an insulating material advantageously this means that neither plugs nor a dual coil fluid line.