a surface treatment with aqueous solutions of k/sub 2/zrf/sub 6/ has been carried out to improve, in dramatic manner, the wetting of carbon (or sic)-base ceramics by liquid light alloys at low temperatures (i.e within the 700 to 900 degrees c range). the mechanism which is thought to be responsible for the wetting improvement involves two steps' (i) k/sub 2/zrf/sub 6/ reacts with aluminium with the formation of k/sub 3/alf/sub 6/, other complex fluoride species and intermetallics, (ii) k/sub 3/alf/sub 6/ dissolves the alumina thin layer, coating the liquid light alloy and enables the wetting of the ceramics. the mechanism has been worked out from sessile drop experiments, solid state chemistry experiments and composite casting. the k/sub 2/zrf/sub 6/ surface treatment appears to be particularly suitable for processing composite materials made of carbon (or sic) fiber preforms and aluminium-base matrices according to techniques directly derived from the light alloy foundry