. ▁ ▁M IM ▁recogn ised ▁that ▁the ▁performance ▁of ▁traditional ▁co pper ▁ref iner ies ▁was ▁const rained ▁by ▁the ▁poor ▁c ath ode ▁geometry ▁inher ent ▁in ▁using ▁co pper ▁st arter ▁sheets . ▁ ▁M IM ▁then ▁developed ▁a ▁research ▁program ▁aim ed ▁at ▁developing ▁similar ▁permanent ▁c ath ode ▁technology ▁for ▁co pper ▁ref ining . ▁C RL ▁had ▁been ▁operating ▁in ▁Town sv ille ▁since ▁ 1 9 5 9 , ▁using ▁conventional ▁st arter - sheet ▁technology ▁and ▁tre ating ▁bl ister ▁co pper ▁produced ▁in ▁the ▁Mount ▁Isa ▁M ines ▁Limited ▁co pper ▁sm elter ▁at ▁Mount ▁Isa ▁in ▁Queensland . ▁C RL ▁incorpor ated ▁the ▁permanent ▁c ath ode ▁technology ▁in ▁its ▁ 1 9 7 8 ▁ref in ery ▁modern isation ▁project . ▁The ▁material ▁initially ▁selected ▁was ▁ 3 1 6 L ▁st ain less ▁steel , ▁st itch - w eld ed ▁to ▁a ▁ 3 0 4 L ▁st ain less - ste el ▁h anger ▁bar . ▁The ▁h anger - bar ▁assembly ▁was ▁then ▁electro pl ated ▁with ▁co pper ▁to ▁a ▁thick ness ▁of ▁ 1 . 3 ▁mill im eters ▁( “ mm ” ) ▁( l ater ▁increased ▁to ▁ 2 . 5   mm ▁and ▁then ▁ 3 . 0   mm ▁to ▁improve ▁the ▁cor ros ion ▁resistance ▁of ▁the ▁h anger ▁bar ) ▁to ▁approximately ▁ 1 5   mm ▁down ▁onto ▁the ▁bla de , ▁which ▁provided ▁sufficient ▁elect rical ▁conduct ivity