Non-chromate conversion coatings

Claim 2

A conversion coating solution which comprises an aqueous solution of from about 0.2 g/l to about 45 g/l of free H 2 SO 4 , from about 1.5 g/l to about 58 g/l of H 2 O 2 , and from about 3 g/l to about 33 g/l of SiO 2 .

Claim 3

The solution of claim 1, wherein the free H 2 SO 4 concentration is between about 1.8 g/l and about 18 g/l.

Claim 4

The solution of claim 1, wherein the H 2 O 2 concentration is between about 7 g/l and about 29 g/l.

Claim 5

The solution of claim 1, wherein the SiO 2 concentration is between about 8 g/l and about 18 g/l.

Claim 6

The solution of claim 1, in which the SiO 2 is provided in the form of sodium silicate or potassium silicate.

Claim 7

The solution of claim 5, wherein the molecular ratio of SiO 2 to either Na 2 O or K 2 O in the sodium silicate or potassium silicate is maintained between about 1 and about 4.

Claim 8

The solution of claim 6, wherein said molecular ratio is at least about 2.2.

Claim 9

The solution of claim 1, containing from about 0.15 g/l to about 10 g/l of a promoter additive or mixtures of promoter additives selected from organophosphorus compounds having the general formula: [X(R.sub.1).sub.m ].sub.n ·[R.sub.2 ].sub.p ·[X(R.sub.1).sub.m [.sub.q, wherein X is a group of the formula ##STR3## in which Z 1 and Z 2 independent from each other are hydrogen, sodium or potassium; m is either 0 or 1; p is either 0 or 1; n+q is either (a) 1 when p=0, or (b) equal to the number of available bonds provided by R 2 when p=1; R 1 is a (a) C 1 -C 4 alkyl or a C 1 -C 4 hydroxy-substituted alkyl and p=0; and (b) C 1 -C 4 alkylene or a C 1 -C 4 hydroxy-substituted alkylene and p=1; R 2 is selected from (a) N≡, m=1 (b) ═N(CH 2 ) r N═, m=1 and r is an integer from 2 to 6 (c) ##STR4## m=1, and (d) a C 1 -C 4 alkylene or a C 1 -C 4 hydroxy-substituted alkylene m=0 or 1.

Claim 10

The solution of claim 8, containing from about 0.5 g/l to about 2 g/l of said organophosphorus compound.

Claim 11

The solution of claim 1 containing from about 0.5 g/l to about 50 g/l of at least one organonitrogen promoter additive slected from the group consisting of thioacetamide, urea, thiourea, N,N'-alkyl substituted ureas and thioureas, cyclic N,N'-alkylene substituted ureas and thioureas, wherein said alkyl and alkylene groups each contain from 1 to 4 carbon atoms.

Claim 12

The solution of claim 10 containing from about 1 g/l to about 10 g/l of said organonitrogen promoter additive.

Claim 13

The solution of claim 9 containing from about 0.5 g/l to about 50 g/l of at least one organonitrogen promoter additive selected from the group consisting of thioacetamide, urea, thiourea, N,N'-alkyl substituted ureas and thioureas, cyclic N,N'-alkylene substituted ureas and thioureas, wherein said alkyl and alkylene groups each contain from 1 to 4 carbon atoms.

Claim 14

The solution of claim 8, wherein the organophosphorus compound is an aminotri(alkylene phosphonic acid).

Claim 15

The solution of claim 8, wherein the organophosphorus compound is a hydroxy alkylene diphosphonic acid.

Claim 16

The solution of claim 8, wherein the organophosphorus compound is a polymethylene diaminetetra(alkylene phosphonic acid).

Claim 17

The solution of claim 8, wherein the organophosphorus compound is a diethylene triaminepenta(alkylene phosphonic acid).

Claim 18

The solution of claim 10, wherein the organonitrogen promoter additive is thioacetamide.

Claim 19

The solution of claim 10, wherein the organonitrogen promoter additive is selected from urea and thiourea.

Claim 20

The solution of claim 10, wherein the organonitrogen promoter additive is selected from N,N'-alkyl substituted ureas and thioureas.

Claim 21

The solution of claim 10, wherein the organonitrogen promoter additive is selected from cyclic N,N'-alkylene substituted ureas and thioureas.

Claim 22

The solution of claim 12, wherein the organonitrogen promoter additive is thiourea.

Claim 23

The solution of claim 12, wherein the organophosphorus compound is 1-hydroxyethylidene-1,1-diphosphonic acid.

Claim 24

The solution of claim 22, wherein the organonitrogen promoter additive is thiourea.

Claim 25

In a process for the formation of corrosion resistant conversion coating onto metallic surfaces selected from zinc, cadmium, silver, copper, aluminum, magnesium and zinc alloys, wherein the metallic surfaces are immersed in a conversion coating solution, and subsequently rinsed and dried, the improvement which comprises: immersing the metallic surfaces into the conversion coating solution of claim 1.

Claim 26

The process of claim 24, in which the metallic surfaces are immersed into the conversion coating solution of claim 8.

Claim 27

The process of claim 24, in which the metallic surfaces are immersed into the conversion coating solution of claim 10.

Claim 28

The process of claim 24, in which the metallic surfaces are immersed into the conversion coating solution of claim 12.

Claim 29

The process of claim 24, in which prior to rinse, the metallic surfaces are immersed for a period of about 5 to about 300 seconds into a second aqueous treatment solution containing from about 0.5 g/l to about 50 g/l of at least one organonitrogen compound selected from the group consisting of thioacetamide, urea, thiourea, N,N'-alkyl substituted ureas and thioureas, cyclic N,N'-alkyl substituted ureas and thioureas, cyclic N,N'-alkylene substituted ureas and thioureas, wherein said alkyl and alkylene groups each contain from 1 to 4 carbon atoms.

Claim 30

The process of claim 25, in which prior to rinse, the metallic surfaces are immersed for a period of about 5 to about 300 seconds into a second aqueous treatment solution containing from about 0.5 g/l to about 50 g/l of at least one organonitrogen compound selected from the group consisting of thioacetamide, urea, thiourea, N,N'-alkyl substituted ureas and thioureas, cyclic N,N'-alkyl substituted ureas and thioureas, cyclic N,N'-alkylene substituted ureas and thioureas, wherein said alkyl and alkylene groups each contain from 1 to 4 carbon atoms.

Claim 31

The process of claim 28 wherein the second aqueous treatment solution also contains from about 0.15 g/l to about 10 g/l of at least one organophosphorus compound having the general formula: [X(R.sub.1).sub.m ].sub.n ·[R.sub.2 ].sub.p ·[X(R.sub.1).sub.m ].sub.q, wherein X is a group of the formula ##STR5## in which Z 1 and Z 2 independent from each other are hydrogen, sodium or potassium; m is either 0 or 1; p is either 0 or 1; n+q is either (a) 1 when p=0, or (b) equal to the number of available bonds provided by R 2 when p=1; R 1 is a (a) C 1 -C 4 alkyl or a C 1 -C 4 hydroxy-substituted alkyl and p=0; and (b) C 1 -C 4 alkylene or a C 1 -C 4 hydroxy-substituted alkylene and p=1; R 2 is selected from (a) N≡, m=1 (b) ═N(CH 2 ) r N═, m=1 and r is an integer from 2 to 6 (c) ##STR6## m=1, and (d) a C 1 -C 4 alkylene or a C 1 -C 4 hydroxy-substituted alkylene, m=0 or 1.

Claim 32

A metallic surface coated by the process of claim 24.

Claim 33

A metallic surface coated by the process of claim 25.

Claim 34

A metallic surface coated by the process of claim 26.

Claim 35

A metallic surface coated by the process of claim 27.

Claim 36

A metallic surface coated by the process of claim 28.

Claim 37

A metallic surface coated by the process of claim 29.

Claim 38

A metallic surface coated by the process of claim 30.

Claim 39

The metallic surface of claim 31, wherein the metal is zinc plate.