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1. WO1981002749 - COMPOSITION FOR INHIBITING CORROSION OF METAL SURFACES

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[ EN ]
15

The invention is hereby claimed as follows:
1. A chromate depositing composition having
a solids content within the range from 0.2 gram per
liter to 75.0 grams per liter, the remainder being water, and" consisting essentially of the following:
Ingredients Grams per Liter
Chromic acid (CrO-j) ,
(expressed as Cr) 0.10-50.0
Hydrofluoric acid (H2F2)
(expressed as F) 0.01-5.0
Fluoboric acid (HBF4)
(expressed as BF4) 0.01-50.0
Sulfuric acid (H2S04)
(expressed as SO4) 0.01-5.0
Hydrofluosilicic acid (^SiFg)
(expressed as SiFg) 0.0-5.0
Additive from the group consisting of: 0.01-saturation zinc oxide, magnesium oxide, solubility at
magnesium hydroxide, aluminum 22°C.
sulfate, aluminum hydroxide and
mixtures thereof
2. A chromate depositing composition as
claimed in claim 1 in which the additive is zinc oxide.
3. A chromate depositing composition as
claimed in claim 1 in which the additive is magnesium
oxide.
4. A chromate depositing composition as
claimed in claim 1 in which the additive is magnesium
hydroxide .

5. A chromate depositing composition as
claimed in claim 1 in which the additive is aluminum
sulfate.
-_i-'
6. A chromate depositing composition as
claimed in claim 1 in which the additive is zinc oxide and the amount corresponds to 1 to 6 grams per liter.

OMPI
^ ™~ - 7. A chromate depositing composition as claimed in claim 1 in which the additive is zinc oxide and the weight ratio of chromic acid to zinc oxide is approximately 2:1.
8. A chromate depositing composition as claimed in claim 1 in which the ratio of the additive to the total acids is such as to give a pH within the range of 1.5 to 3.6 at 22 °C. and a chromate concentration of 0.05 to 10.0 grams per liter, as Cr.
9. A process for treating ferrous or non-ferrous metal surfaced articles to improve corrosion resistance and receptivity to synthetic resin coatings which comprises bringing said surface into contact with a chromate depositing solution containing as essential components hexavalent chromium but no trivalent chromium, together with fluoboric acid, hydrofluoric acid, sulfuric acid with or without hydrofluosilicic acid, said solution also containing as an additive zinc oxide and/or magnesium oxide, and/or magnesium hydroxide, and/or aluminum sulfate, and/or aluminum hydroxide.:, the ratio of said additive to the total acids being such as to give a pH within the range of 1,5 to 3,6 at 22°C. and a chromate concentration of 0.05 to 10.0 grams per liter, as Cr, the remainder being water, and consisting essen-tially of the following:
Ingredients Grams per Liter
Chromic acid (Crθ3)
(expressed as Cr) 0.10-50.0
Hydrofluoric acid (H2F2)
(expressed as F) 0.01-5.0
Fluoboric _acid_,(_HBF4) 0.01-50.0
(expressed as BF4)
Sulf ric acid .(H2SO4 ) 0.01-5.0
(expressed as SO4)
Hydrofluosilicic acid (H2SiFg)
(expressed as SiFg) 0.0-5.0
of : 0.01-saturation zinc oxide, magnesium oxide, solubility at magnesium hydroxide, aluminum 22°C.
sulfate, aluminum hydroxide and
mixtures thereof 17

10. A process for treating ferrous or non-ferrous metal surfaced articles as claimed in claim 9 in which the additive is zinc oxide,
11. A process for treating ferrous or non-ferrous metal surfaced articles as claimed in claim 9 in which the additive is magnesium oxide,
12. A process for treating ferrous or non-ferrous metal surfaced articles as claimed in claim 9 in which the additive is magnesium hydroxide,
13 , A process for treating ferrous or non-ferrous metal surfaced articles as claimed in claim 9 in which the additive is aluminum sulfate.
14. A process as claimed in claim 9 in which the metal surfaced article is dried without rinsing and a coating composition which dries to a water resistant film is applied thereto.
15. A process as claimed in claim 14 in which the coating composition is an acrylic resin coating composition.
16. A process as claimed in claim 9 in which said ferrous and non-ferrous metals are from the group consisting of cold rolled steel, aluminized and. galvanized iron and steel, aluminum, aluminum-zinc alloys, magnesium and magnesium-aluminum alloys.
17. A process as claimed in claim 9 in which said metal surfaced articles are in the form of sheets, coils, wires, tubes or rods which are brought into contact with said chromate depositing solution at a linear speed" of at least 50 feet per minute, the said solution being effective to deposit at least 0.2 mg/ square foot of chromate, as Cr.

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18. A process as claimed in claim 9 in which the additive is zinc oxide and the weight ratio of chromic acid to zinc oxide is approximately 2:1.
19. A process as claimed in claim 9 in which the metal is aluminum and the ratio of the additive to the total acids is such as to give a pH within the range of 1.8 to 3.5 at 22°C.
20. A process as claimed in claim 9 in which the metal is galvanized iron or steel and the ratio of the additive to the total acids is such as to give a pH within the range of 1.8 to 3,5 at 22°C.
21. A process as claimed in claim 9 in which the metal is cold rolled steel and the ratio of the additive to the total acids is such as to give a pH within the range of 1.8 to 3.5 at 22°C. and the composition contains hydrofluosilicic acid.
22. A ferrous or non-ferrous metal surfaced article resulting from the process of claim 9.
23. An article as claimed in claim 22 over-coated with a coating composition which dries to a water resistant film.