Corrosion inhibitor

Abstract

A corrosion inhibitor for use with Urea Ammonium Nitrate solutions is disclosed, comprising a blend of molybdate and one or more of the inorganic phosphates (including phosphates, polyphosphates, and pyrophosphates) and organic phosphates or phosphonates. Inorganic phosphates include, but are not limited to, SHMP (Sodium Hexametaphosphate) and TKPP (Tetra-Potassium Pyrophosphate). Phosphoric acid may also be utilized to provide phosphate ions, by itself or in combination with other phosphorous containing compounds as a secondary inhibitor. There are numerous other inorganic phosphates that will also serve as suitable secondary inhibitors. Organic phosphates or phosphonates include, but are not limited to, HEDP (1-Hydroxyethylidine-1,1-diphosphonic acid; also known as ethanol diphosphonate, acetodiphosphonic acid, or etidronic acid), ATMP (aminotri(methylenephosphonic acid)), PBTC (Phosphonobutane tricarboxylic acid), DETPMP (Diethylenetriaminepenta(methylene phosphonic acid)), and HPA (hydroxyphosphono acetic acid). There are numerous other organic phosphates and phosphonates that will also serve as suitable secondary inhibitors. The amount of molybdate can range from 1 ppm to 500 ppm by weight of fertilizer solution, with the preferred range from 10 ppm to 200 ppm. Amounts of inorganic or organic phosphate can also range from levels as low as 1 ppm up to 500 ppm, with the preferred range being from 5 ppm to 50 ppm.

1 . A corrosion inhibiting solution for use with Urea Ammonium Nitrate solutions consisting of: an aqueous solution of molybdate ion and at least one of the phosphorous containing compounds selected from the group consisting of phosphoric acid, organic phosphates, organic phosphonates, and inorganic phosphates whereby said aqueous solution can be combined with Urea Ammonium Nitrate solutions to provide between 1 ppm and 500 ppm of said molybdate ion by weight of Urea Ammonium Nitrate solution, and between 1 ppm and 500 ppm of said at least one of the phosphorous containing compounds by weight of Urea Ammonium Nitrate solution.  
   
   
       2 : A corrosion inhibiting solution as in  claim 1  wherein said inorganic phosphate is at least one of the compounds selected from the group consisting of Sodium Hexametaphosphate and Tetra-Potassium Pyrophosphate.  
   
   
       3 : A corrosion inhibiting solution as in  claim 1  wherein said at least one of the phosphorous containing compounds is at least one of the compounds selected from the group consisting of HEDP (1-Hydroxyethylidine-1,1-diphosphonic acid; also known as ethanol diphosphonate, acetodiphosphonic acid, or etidronic acid), ATMP (aminotri(methylenephosphonic acid)), PBTC (Phosphonobutane tricarboxylic acid), DETPMP (Diethylenetriaminepenta(methylene phosphonic acid)), and HPA (hydroxyphosphono acetic acid).  
   
   
       4 : A corrosion inhibiting solution as in  claim 1  wherein said at least one of the phosphorous containing compounds is a mixture of phosphoric acid and inorganic phosphates.  
   
   
       5 : A corrosion inhibiting solution as in  claim 1  wherein said at least one of the phosphorous containing compounds is a mixture of phosphoric acid and organic phosphates.  
   
   
       6 : A corrosion inhibiting solution as in  claim 1  wherein said at least one of the phosphorous containing compounds is a mixture of phosphoric acid and inorganic and organic phosphates.  
   
   
       7 : A corrosion inhibiting solution as in  claim 1  wherein said molybdate ion is added to said aqueous solution in the form of an alkali metal molybdate.  
   
   
       8 : A corrosion inhibiting solution as in  claim 1  wherein said molybdate ion is added to said aqueous solution in the form of sodium molybdate.  
   
   
       9 : A corrosion inhibiting solution for use with Urea Ammonium Nitrate solutions consisting of: an aqueous solution of molybdate ion and at least one of the phosphorous containing compounds selected from the group consisting of phosphoric acid, organic phosphates, organic phosphonates, and inorganic phosphates whereby said aqueous solution can be combined with Urea Ammonium Nitrate solutions to provide between 10 ppm and 200 ppm of said molybdate ion by weight of Urea Ammonium Nitrate solution, and between 5 ppm and 50 ppm of said at_least one of the phosphorous containing compounds by weight of Urea Ammonium Nitrate solution.  
   
   
       10 : A corrosion inhibiting solution as in  claim 9  wherein said at least one of the phosphorous containing compounds is at least one of the compounds selected from the group consisting of Sodium Hexametaphosphate, Tetra-Potassium Pyrophosphate, HEDP (1-Hydroxyethylidine-1,1-diphosphonic acid; also known as ethanol diphosphonate, acetodiphosphonic acid, or etidronic acid), ATMP (aminotri(methylenephosphonic acid)), PBTC (Phosphonobutane tricarboxylic acid), DETPMP (Diethylenetriaminepenta(methylene phosphonic acid)), and HPA (hydroxyphosphono acetic acid).  
   
   
       11 : A corrosion inhibiting solution as in  claim 9  wherein said molybdate ion is added to said aqueous solution in the form of an alkali metal molybdate.  
   
   
       12 : A corrosion inhibiting solution as in  claim 9  wherein said molybdate ion is added to said aqueous solution in the form of sodium molybdate.  
   
   
       13 : A corrosion inhibiting solution as in  claim 9  wherein said at least one of the phosphorous containing compounds is a mixture of phosphoric acid and inorganic phosphates.  
   
   
       14 : A corrosion inhibiting solution as in  claim 9  wherein said at least one of the phosphorous containing compounds is a mixture of phosphoric acid and organic phosphates.  
   
   
       15 : A corrosion inhibiting solution as in  claim 9  wherein said at least one of the phosphorous containing compounds is a mixture of phosphoric acid and inorganic and organic phosphates.