Coatings for corrosion susceptible substrates

1. A coating composition for application to a metal substrate for protection against corrosion, the composition comprising an aqueous dispersion of at least one water dispersible lower alkoxysilane carrying an epoxy group, and a water dispersible aromatic diamine reactive curing agent for coating onto a corrosion-susceptible substrate and curing in situ on the substrate to form a corrosion resistant protective coating thereon.

2. The coating composition of claim 1 , wherein the aromatic diamine curing agent is a benzene diamine.

3. The coating composition of claim 2 , wherein the benzene diamine is at least one phenylenediamine.

4. The coating composition of claim 3 , wherein the phenylenediamine is ortho-phenylenediamine, meta-phenylenediamine or para-phenylenediamine.

5. The coating composition of claim 1 , wherein the aromatic diamine curing agent is a mixture of at least two of ortho-phenylenediamine, meta-phenylenediamine and para-phenylenediamine.

6. The coating composition of claim 1 , wherein the at least one lower alkoxysilane comprises a combination of an epoxy group carrying silane and a second lower alkoxysilane.

7. The coating composition of claim 1 , wherein the lower alkoxysilane carrying an epoxy group is 3-glycidoxypropyltrimethoxysilane, 3-glycidyloxypropyltriethoxysilane, 3-glycidyloxypropyltrichlorosilane, diethoxy(3-(glycidyloxy)propyl)methylsilane, dichloro(3-(glycidyloxy)propyl)methylsilane, 6-glycidyloxyhexyltriethoxysilane, or 6-glycidyloxyhexyltrimethoxysilane.

8. The coating composition of claim 7 , wherein the lower alkoxysilane carrying an epoxy group is 3-glycidyloxypropyl trimethoxysilane.

9. The coating composition of claim 6 , wherein the second lower alkoxysilane is tetraethoxysilane, tetramethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, aminopropyltrimethoxysilane, aminopropyltriethoxysilane, methylaminopropyldimethoxysilane, methylaminopropyldiethoxysilane, dimethylaminopropylmethoxysilane or dimethylaminopropylethoxysilane.

10. The coating composition of claim 9 , wherein the second lower alkoxysilane is tetraethoxysilane or tetramethoxysilane.

11. The coating composition of claim 1 , wherein the metal substrate is steel.

12. The coating composition of claim 1 , wherein the metal substrate is aluminum or alloys thereof.

13. A process of preparing a corrosion resistant protective coating on a corrosion susceptible substrate, which comprises forming an aqueous suspension of a lower alkoxysilane containing epoxy groups and an aromatic diamine reactive curing agent, applying said aqueous suspension to the substrate, and polymerizing and curing the lower alkoxysilane by sol-gel process to form a corrosion resistant protective coating on the substrate.

14. The process of claim 13 , wherein the aromatic diamine curing agent is a benzene diamine.

15. The process of claim 14 , wherein the benzene diamine is at least one phenylenediamine.

16. The process of claim 15 , wherein the phenylenediamine is ortho-phenylenediamine, meta-phenylenediamine or para-phenylenediamine.

17. The process of claim 15 , wherein the aromatic diamine curing agent is a mixture of at least two of ortho-phenylenediamine, meta-phenylenediamine and para-phenylenediamine.

18. The process of claim 13 , wherein the alkoxysilane polymer of the coating is a combination of an epoxy group carrying silane and a second lower alkoxysilane.

19. The process of claim 13 , wherein the lower alkoxysilane carrying an epoxy group is 3-glycidoxypropyltrimethoxysilane, 3-glycidyloxypropyltriethoxysilane, 3-glycidyloxypropyltrichlorosilane, diethoxy(3-(glycidyloxy)propyl)methylsilane, dichloro(3-(glycidyloxy)propyl)methylsilane, 6-glycidyloxyhexyltriethoxysilane, or 6-glycidyloxyhexyltrimethoxysilane.

20. The process of claim 13 , wherein the lower alkoxysilane carrying an epoxy group is 3-glycidyloxypropyl trimethoxysilane.

21. The process of claim 18 , wherein the second lower alkoxysilane is tetraethoxysilane, tetramethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, aminopropyltrimethoxysilane, aminopropyltriethoxysilane, methylaminopropyldimethoxysilane, methylaminopropyldiethoxysilane, dimethylaminopropylmethoxysilane or dimethylaminopropylethoxysilane.

22. The process of claim 18 , wherein the second lower alkoxysilane is tetraethoxysilane or tetramethoxysilane.

23. The process of claim 13 , wherein the corrosion susceptible substrate is steel.

24. The process of claim 13 , wherein the corrosion susceptible substrate is aluminum or alloys thereof.

25. The process of claim 13 , wherein the aqueous suspension of the lower alkoxysilane containing epoxy groups has a water to silane ratio of from about 10:1 to about 25:1.

26. The process of claim 13 , wherein the aqueous suspension of the lower alkoxysilane containing epoxy groups has a water to silane ratio of about 15:1.

27. The process of claim 13 , wherein the process is conducted at about room temperature.

28. A process of preparing a corrosion resistant protective coating on a corrosion susceptible substrate, which comprises applying to the corrosion susceptible substrate an aqueous suspension of a polymerized or polymerizable lower alkoxysilane containing epoxy groups, forming a coating on the corrosion susceptible substrate of said lower alkoxysilane and curing the polymer coating on the corrosion susceptible substrate by reaction with an aromatic diamine reactive curing agent.

29. The process of claim 28 , wherein the aromatic diamine curing agent is a benzene diamine.

30. The process of claim 29 , wherein the benzene diamine is at least one phenylenediamine.

31. The process of claim 29 , wherein the phenylenediamine is ortho-phenylenediamine, meta-phenylenediamine or para-phenylenediamine.

32. The process of claim 28 , wherein the aromatic diamine curing agent is a mixture of at least two of ortho-phenylenediamine, meta-phenylenediamine and para-phenylenediamine.

33. The process of claim 28 , wherein the lower alkoxysilane carrying an epoxy group is 3-glycidoxypropyltrimethoxysilane, 3-glycidyloxypropyltriethoxysilane, 3-glycidyloxypropyltrichlorosilane, diethoxy(3-(glycidyloxy)propyl)methylsilane, dichloro(3-(glycidyloxy)propyl)methylsilane, 6-glycidyloxyhexyltriethoxysilane, or 6-glycidyloxyhexyltrimethoxysilane.

34. The process of claim 28 , wherein the lower alkoxysilane carrying an epoxy group is 3-glycidyloxypropyl trimethoxysilane.

35. The process of claim 28 , wherein the corrosion susceptible substrate is steel.

36. The process of claim 28 wherein the corrosion susceptible substrate is aluminum or alloys thereof.

37. The process of claim 28 , wherein the aqueous suspension of the lower alkoxysilane containing epoxy groups has a water to silane ratio of from about 10:1 to about 25:1.

38. The process of claim 28 , wherein the aqueous suspension of the lower alkoxysilane containing epoxy groups has a water to silane ratio of about 15:1.

39. The process of claim 28 , wherein the process is conducted at about room temperature.

40. The process of claim 28 , wherein the polymer curing reaction is conducted at about room temperature.