Method and compositions for penetrating and removing accumulated corrosion products and deposits from metal surfaces

Claim 1

A method of removing accumulated iron oxide deposits from the metal surfaces in contact with the water of a cooling water system while leaving a protective metal layer intact, said method occurring without shutting the cooling water system down and comprising the steps of: a. maintaining the pH of said water within the range of from about 6.5 to about 7.5 throughout the entire method; b. pretreating said surfaces by adding from about 25-500 ppm of an organic reductant/chelant selected from the group consisting of pyrogallol and methyl gallate to said cooling water, based upon one million parts of said cooling water, for a time sufficient to reduce or complex the iron in said deposits, thereby softening and converting said deposits into a water soluble form; c. subsequently contacting said surfaces with from about 100-2000 ppm of an inorganic reducing agent adapted to reduce any remaining iron ions and, at the same time, regenerate said organic reductant/chelant; d. maintaining from about 1 to 20 ppm of a surfactant in said water during both said steps (b) and (c) to reduce losses of said organic reductant/chelant and said inorganic reducing agent, and e. blowing down said cooling water to remove said soluble deposits.

Claim 2

A method of removing accumulated iron oxide deposits from the metal surfaces in contact with the water of a cooling water system while leaving a protective metal layer intact, said method occurring without shutting the cooling water system down and comprising the steps of: a. maintaining the pH of said water within the range of from about 6.5 to about 7.5 throughout the entire method; b. pretreating said surfaces by adding from about 25-500 ppm of an organic reductant/chelant selected from the group consisting of pyrogallol and methyl gallate to said cooling water, based upon one million parts of said cooling water, for a time sufficient to reduce or complex the iron in said deposits, thereby softening and converting said deposits into a water soluble form; c. subsequently contacting said surfaces with from about 100-2000 ppm of an inorganic reducing agent adapted to reduce any remaining iron ions and, at the same time, regenerate said organic reductant/chelant; d. maintaining from about 1 to 20 ppm of a surfactant in said water during both said steps (b) and (c) to reduce losses of said organic reductant/chelant and said inorganic reducing agent, and e. blowing down said cooling water to remove said soluble deposits.