A centrifugal separator for non-cohesive particulates, such as are found in transmission oils and hydraulic liquids, consists of a housing 11 enclosing a vertical spindle 16 on which spins a liquid reaction driven rotor container 20. The container is divided internally by inwardly extending partition wall 35 into separate outflow chambers 36 and 37. Non-cohesive particulates which separate from the liquid, and are held against the peripheral side wall 24 1 by centrifugal force during rotation, slump therefrom in the absence of rotation and risk forming a slurry that gets carried to the outflow chamber. Barrier means 140 consists of a upwardly extending, outwardly inclined barrier wall 141 forming a contaminant retention region 144 with a restricted neck 143 defined by the separation of the barrier wall edge 142 from the side wall, that permits deposits on the barrier wall to carry to the peripheral side wall and spread across it during rotation, does not interfere with slumping absent rotation and inhibits the slumped material from being washed into the outflow before rotation recommences.