Branched alkyl acrylamide types of polymer-zinc corrosion inhibitor

A method of preventing corrosion and scale formation on metals exposed to industrial recirculating waters having a pH ranging between about 7.0 to about 9.5, which consists essentially of adding to said industrial recirculating waters an effective amount of a combination of a water-soluble zinc salt, a nitrogen-containing N-alkylated acrylamide zinc complexing polymer and an orthophosphate ion source, wherein: (a) the weight ratio of zinc to nitrogen-containing zinc complexing polymer ranges between 1:1 to about 1:20; (b) the nitrogen-containing N-alkylated acrylamide zinc complexing polymer has a weight average molecular weight ranging between 2,000 to 25,000 and is selected form the group consisting of water-soluble copolymers and terpolymers containing at least two mole percent of an N-alkylated acrylamide monomer, wherein the nitrogen substituted alkyl group contains from 3-12 carbon atoms and wherein the N-alkyl group may be linear or branched.