Tile & Grout Restorer is a concentrated blend of acids, chelating and wetting agents that can clean and brighten dirty, discolored grout lines and remove soil, hard water stains, lime build-up, and soap scum from ceramic tile surfaces. PH: 1.5 A chelating agent is a substance whose molecules can form several bonds to a single metal ion. In other words, a chelating agent is a multidentate ligand. An example of a simple chelating agent is ethylenediamine. ethylenediamine.