Tri-sodium Phosphate is a powerful phosphate cleaning agent and has many uses, some of which are listed below: It is used for cleaning degreg exterior or internal surfaces before painting. It should be mixed depending of the level of cleaning needed for medium strength cleaning use 1 2 a cup of tri-sodium phosphate added to 9 litres of warm water, for heavy duty cleaning use 1 cup of tri-sodium phosphate added to 4 litres of warm water. When using a Tri-Sodium Phosphate solution for cleaning, please aviod extensive use in the bathroom, as it can stain metal surfaces and ceramic tiles. Also aviod contact with wood as staining might also occur. Tri-Sodium Phosphate is also used as flux for hard soldering joints.Mixed with chlorine bleach is excellent for removing mildew on wood without whitening the wood. Cleaning agent stain remover degreaser. Great for cleaning surfaces before painting. 99 Pure Tri-Sodium Phosphate.