Patent ID: 8062435

Claim:
An improved phosphating operation wherein metal substrates are either A. contacted in a bath A with a working phosphating composition A comprised of water, dissolved phosphate anions, dissolved NCM cations, and dissolved zinc cations, wherein said bath A additionally contains at least one piece of process equipment having a surface, and wherein a relatively hard, adherent, and difficult to remove scale forms on said surface when said surface is in contact with said working phosphating composition A for an extended period of time; or B. continually passed at a high rate of speed through a bath B containing a working phosphating composition B comprised of water, dissolved phosphate anions, dissolved NCM cations and dissolved zinc cations, wherein a replenisher composition comprised of zinc cations is periodically added to said working phosphating composition and wherein sludge forms in bath B following such addition of the replenisher composition; the improvement comprising said working phosphating composition A or said working phosphating composition B comprising a concentration of dissolved zinc cations that is not greater than 0.08 wt. %, wherein the ratio of dissolved zinc cations to dissolved NCM cations is not more than 0.5:1.00, and maintaining a level of dissolved ferric cations in said working phosphating composition A or said working phosphating composition B which is effective to either reduce the amount of scale forming on said surface or reduce the amount of sludge forming in bath B in said working phosphating composition A or working phosphating composition B, wherein working phosphating composition A or working phosphating composition B is maintained at a temperature of at least 66° C.