The cooling water chemistry has changed steadily over the past decade. Use of high performance antiscalants, corrosion inhibitors, polymer for better dispersion, total prevention of microbial deposits by using powerful biocides and biodispersants, pH boosters and advanced hardness stabilizers is the current practice. But addition of so many different chemicals to the cooling water system (CWS) makes the cooling water chemistry so complex and complicated that it is very difficult to control it by the operator. A clear understanding about the contribution of antiscalant and zinc ions separately towards the corrosion control in a CWS is required. In the present work, a single antiscalant (trisodium phosphate) was tried which may control scaling as well as corrosion problem in CWS. Weight loss and electrochemical polarization technique have been carried out at different temperatures using various concentration of the inhibitor. Mechanism of inhibition is explained on the basis of molecular structure of the inhibitor. The inhibitor provides good inhibition efficiency and acts as anodic inhibitor when present alone and mixed inhibitor with zinc ions. Moreover, addition of zinc ions to cooling water along with inhibitor, do not increase inhibition efficiency of inhibitor to an appreciable extent.