Corrosion inhibitor composition applicable for aluminum and steel protection and procedure

Abstract

A corrosion-inhibiting composition for application to a metal substrate, such as aluminum or steel, and in connection with a paint, and the synthesis of the composition is disclosed. The base of the inhibitor can be selected from the group consisting of 2,5-dimercapto-1,3,4 thiadiazole (DMTD), 2,4-dimercapto-s-triazolo-[4,3-b]-1,3-4-thiadiazole, trithiocyanuric acid (TMT), and derivatives of DMTD and TMT, including various N—,S— and N,N—, S,S— and N,S— substituted derivatives of DMTD, various S-substituted derivatives of Trithiocyanuric acid, 5,5 dithio-bis (1,3,4 thiadiazole-2(3H)-thione or (DMTD) 2 or (DMTD) n the polymer of DMTD, dimer and polymers of TMT, Salts of DMTD of the general formula: M(DMTD) n where n=1,2 or 3, and M is a metal cation and preferable M=Zn(II), Bi(III), Co(II), Ni(II), Cd(II), Pb(II), Ag(I), Sb(III), or Cu(II) (examples: ZnDMTD, Zn(DMTD) 2 , Bi(DMTD) 3 ) , similar salts of TMT , as for example, ZnTMT, in a ratio of 1:1, salts of (DMTD) n of general formula M[(DMTD) n ] m , where n=2 or n>2, m=1,2, or 3 and M is as above specified. Typical examples are: Zn[(DMTD) 2 ], Zn[(DMTD) 2 ] 2 , aryl or alkyl ammonium salts of DMTD or (DMTD) n , similar salts of TMT, quaternary ammonium salts of DMTD or (DMTD) n , and TMT, poly-ammonium salt of DMTD or (DMTD) n and TMT formed with polyamines; inherently conductive polyaniline doped with DMTD or (DMTD) 2 and TMT ; inherently conductive polypyrrol and/or polythiophen doped with DMTD, (DMTD) 2 and/or TMT, micro or nano composites of poly DMTD/ polyaniline, poly DMTD/polypyrrol ,and poly DMTD/polythiophen, similar micro or nano composites with TMT DMTD or salts of DMTD or derivatives of DMTD and of TMT, as constituents of various pigment grade inorganic matrixes or physical mixtures, DMTD or salts of DMTD or derivatives of DMTD and TMT in encapsulated forms, such as: inclusions in various polymer matrices, or as cyclodextrin-inclusion compounds or microencapsulated form.

What is claimed is:  
     
         1 . A process for protecting an aluminum substrate against atmospheric corrosion comprising: 
 providing an aluminum surface to be protected,    applying a coating to said surface of a protective material selected from a group consisting of di-mercapto and poly-mercapto compounds and their derivatives, said coating substance having a limited solubility in water of between about 0.01 and about 1000 mmoles/per liter of water.    
     
     
         2 . A process for protecting an aluminum substrate against atmospheric corrosion comprising: 
 providing an aluminum surface to be protected,    applying a coating to said surface of less than approximately 20 microns in thickness of a protective material selected from a group consisting of di-mercapto and poly-mercapto compounds and their derivatives, said coating substance having a limited solubility in water of between about 0.01 and about 1000 mmoles/per liter of water.    
     
     
         3 . A process according to  claim 1  wherein said coating substance has a limited solubility in water of between about 0.1 and about 10 mmoles/per liter of water.  
     
     
         4 . A process according to  claim 1  wherein said coating substance is applied as a saturated solution and is subsequently dried whereby a conversion coating is formed on said substrate, said conversion coating being subsequently coated with a paint.  
     
     
         5 . A process according to  claim 1  wherein said coating substance is incorporated into a silane-based gel coating.  
     
     
         6 . A process according to  claim 1  wherein saidsubstance is selected from the group consisting of 2,5-dimercapto-1,3,4 thiadiazole (DMTD), 2,4-dimercapto-s-triazolo-[4,3-b]-1,3-4-thiadiazole, trithiocyanuric acid (TMT), derivatives of DMTD and derivatives of TMT.  
     
     
         7 . A process according to  claim 1  wherein said substance is selected from the group consisting of 2,5-dimercapto-1,2,4 thiadiazole; 2,4-dimercapto-s-triazolo-[4,3-b]-1,3-4-thiadiazole; 5,5 dithio-bis (1,3,4 thiadiazole-2(3H)-thione and (DMTD) 2 ; (DMTD) n ; M(DMTD) n  where n=1,2 or 3, and M is a metal cation selected from the group consisting of Zn, Bi, Co, Ni, Cd, Pb, Ag, Sb, or Cu; aryl ammonium salts of DMTD; aryl ammonium salts of (DMTD) n ; alkyl ammonium salts of (DMTD),; quaternary ammonium salts of DMTD; quaternary ammonium salts of (DMTD) n ; polyaniline, polythiophen, and polypyrrol doped with DMTD; polyaniline, polythiophen, and polypyrrol doped with (DMTD) 2  and micro and nano composites of poly DMTD/polyaniline, DMTD polythiophen and poly DMTD/polypyrrol.  
     
     
         8 . A process according to  claim 1  wherein said coating substance is applied by incorporating the same in a curable polymeric coating composition and applying said composition over said substrate.  
     
     
         9 . A process according to  claim 1  wherein said coating substance is selected from the group consisting of: 2,5-dimercapto-1,3,4 thiadiazole (DMTD); 2,4-dimercapto-s-triazolo-[4,3-b]-1,3-4-thiadiazole; an organic derivative of DMTD; N—, S— and N, N—, S— and N, S-substituted derivatives of DMTD, 5,5 dithio-bis(1,3,4 thiadiazole-2(3H)-thione or (DMTD) 2  or (DMTD) n  a polymer of DMTD; a salt of DMTD of general formula, M(DMTD) n , where n=1,2 or 3, and M is a metal cation and M=Zn, Bi, Co, Ni, Cd, Pb, Ag, Sb, or Cu; a salt of (DMTD) n  of general formula M[(DMTD) n ] m , where n=2 or n>2, m=1,2, or 3 and M=Zn, Bi, Co, Ni, Cd, Pb, Ag, Sb, or Cu; aryl and alkyl ammonium salts of DMTD and (DMTD) n ; quaternary ammonium salts of DMTD and(DMTD) n ; polyammonium salts of DMTD and (DMTD) n  formed with a polyamines; polyaniline, polypyrrol and polythiophen doped with DMTD; polyaniline, polypyrrol and polythiophen doped with (DMTD) 2 ; a micro and nano composites of poly DMTD/polyaniline, poly DMTD/polypyrrol, and poly DMTD/polythiophen; DMTD , salts of DMTD , and derivatives of DMTD, as constituents of an inorganic matrix; DMTD , salts of DMTD ,and derivatives of DMTD encapsulated form in a polymer matrix, or as a cyclodextrin-inclusion compound; and a combination of said forms.  
     
     
         10 . A process according to  claim 1  wherein said coating substance is selected from the group consisting of: 
 Trithiocyanuric acid (TMT); S-substituted derivatives of TMT; a salt of TMT of general formula, M(TMT) n , where n=1,2 or 3, and M is a metal cation and M=Zn, Bi, Co, Ni, Cd, Pb, Ag, Sb, or Cu; aryl and alkyl ammonium salts of TMT; quaternary ammonium salts of TMT; polyamines formed with TMT; polyaniline doped with TMT; polypyrroline and polythiophen doped with TMT; micro and nano composites of poly TMT/polyaniline, poly TMT/polypyrrolidone, and poly TMT/polythiophen; TMT, salts of TMT, and derivatives of TMT, as constituents of an inorganic matrix; salts of DMTD ,and derivatives of TMT encapsulated form in a polymer matrix, or as a cyclodextrin-inclusion compound; and a combination of said forms.  
 
     
     
         11 . The coating substance of  claim 1  wherein the coating substance is used in a paint.  
     
     
         12 . The paint according to  claim 9 , whereby the paint is applied to an aluminum surface.  
     
     
         13 . A process for protecting a steel substrate against atmospheric corrosion comprising: 
 providing a steel surface to be protected,    applying a coating to said surface of less than approximately 20 microns in thickness of a protective material selected from TMT and TMT derivatives.    
     
     
         14 . A process according to  claim 11  wherein said coating substance is applied as a saturated solution and is subsequently dried whereby a conversion coating is formed on said substrate, said coating being subsequently coated with a paint.  
     
     
         15 . A process according to  claim 11  wherein said coating substance is incorporated into a silane-based gel coating.  
     
     
         16 . A process according to  claim 11  wherein said coating substance is selected from the group consisting of: 
 Trithiocyanuric acid (TMT); S-substituted derivatives of TMT; a salt of TMT of general formula, M(TMT) n , where n=1,2 or 3, and M is a metal cation and M=Zn, Bi, Co, Ni, Cd, Pb, Ag, Sb, or Cu; aryl and alkyl ammonium salts of TMT; quaternary ammonium salts of TMT; polyamines formed with TMT; polyaniline doped with TMT; polypyrroline and polythiophen doped with TMT; micro and nano composites of poly TMT/polyaniline, poly TMT/polypyrrolidone, and poly TMT/polythiophen; TMT, salts of TMT, and derivatives of TMT, as constituents of an inorganic matrix; salts of DMTD ,and derivatives of TMT encapsulated form in a polymer matrix, or as a cyclodextrin-inclusion compound; and a combination of said forms.  
 
     
     
         17 . The steel substrate of  claim 11 , wherein said steel substrate comprises a galvanized steel.  
     
     
         18 . The coating substance of  claim 11 , wherein the coating substance is used in a paint.  
     
     
         19 . The paint according to  claim 14 , whereby the paint is applied to a steel surface.  
     
     
         20 . The paint according to  claim 14 , whereby said paint is applied to a galvanized steel surface.