Corrosion inhibitors in polyurea coatings

Abstract

Durable elastomeric polyurea coatings can be applied to metal surfaces subjected to impacts and environmental corrosion. Corrosion resistance of the coatings, especially on magnesium alloy surfaces, is improved by incorporation of particulate inhibitor additives in the liquid polyurea precursor coating material. Examples of inhibitors include potassium dichromate, sodium dichromate, potassium permanganate, vanadium pentoxide, phosphorus anhydride, cerium oxide, lanthanum oxide, calcium oxide and sodium oxide.

1 . A coating material for a magnesium alloy surface of an article, the coating material comprising: 
 liquid precursors of an elastomeric polyurea formulated for spray coating or immersion coating of the magnesium alloy surface, the precursors containing particles of a corrosion inhibitor for the magnesium alloy.    
     
     
         2 . A coating material for a magnesium alloy surface as recited in  claim 1  in which the corrosion inhibitor is at least one of potassium dichromate, sodium dichromate, potassium permanganate, vanadium pentoxide, and phosphorus anhydride.  
     
     
         3 . A coating material for a magnesium alloy surface as recited in  claim 1  in which the corrosion inhibitor is at least one of cerium oxide and lanthanum oxide.  
     
     
         4 . A coating material for a magnesium alloy surface as recited in  claim 1  in which the corrosion inhibitor is at least one of calcium oxide and sodium oxide.  
     
     
         5 . A coating material for a magnesium alloy surface as recited in  claim 1  in which the polyurea comprises the 4, 4′ isomer and 2, 4′ isomer of methylene bisphenyl isocyanate.  
     
     
         6 . A component for an automotive vehicle, the component comprising a magnesium alloy surface with a coating of an elastomeric polyurea, the elastomeric polyurea comprising particles of a corrosion inhibitor for the magnesium alloy in an amount up to about one percent by weight of the polyurea.  
     
     
         7 . A component for an automotive vehicle as recited in  claim 6  in which the corrosion inhibitor is at least one of potassium dichromate, sodium dichromate, potassium permanganate, vanadium pentoxide, and phosphorus anhydride.  
     
     
         8 . A component for an automotive vehicle as recited in  claim 6  in which the corrosion inhibitor is at least one of cerium oxide and lanthanum oxide.  
     
     
         9 . A component for an automotive vehicle in which the corrosion inhibitor is at least one of calcium oxide and sodium oxide.  
     
     
         10 . A component for an automotive vehicle in which the polyurea comprises the 4, 4′ isomer and 2, 4′ isomer of methylene bisphenyl isocyanate.