Conversion coating composition, surface treated steel sheet, and method for manufacturing the same
A conversion coating composition comprising 0.01 wt % to 0.2 wt % of phosphorous (P); 0.01 wt % to 0.2 wt % of magnesium (Mg); 0.005 wt % to 0.15 wt % of zirconium (Zr); 0.005 wt % to 0.15 wt % of titanium (Ti); 0.005 wt % to 0.15 wt % of vanadium (V); 0.05 wt % to 1 wt % of phenol resin; the balance of water and other unavoidable impurities is provided. A surface treated steel sheet comprising a base steel sheet; a zinc or zinc alloy plated layer formed on the base steel sheet; a blackening layer formed on the zinc or zinc alloy plated layer; and an organic and inorganic complex conversion coating layer formed on the blackening layer, wherein the organic and inorganic complex conversion coating layer may satisfy the weight ratio of P:Mg:Zr:Ti:V=1:0.045 to 2:0.035 to 1.5:0.035 to 1.3:0.035 to 1.5 (based on the weight of P) is also provided. A method for manufacturing a steel sheet treated with the conversion coating composition is also provided.
1. A surface treated steel sheet comprising:
a base steel sheet;
a zinc or zinc alloy plated layer formed on the base steel sheet;
a blackened film formed on the zinc or zinc alloy plated layer; and
an organic and inorganic composite conversion coating film formed on the blackened film,
wherein the organic and inorganic composite conversion coating film satisfies the weight ratio of P:Mg:Zr:Ti:V=1:0.045-2:0.035-1.5:0.035-1.3:0.035-1.5 (based on P),
wherein the blackened film satisfies the atomic ratios of Zn:M:O=1:0.01-0.065: 0.1-0.5 (based on atomic Zn), and
where M is one or more element selected from the group consisting of Mg, Al, Zn, Fe, Ni, Co, Mn, Ti, Sn, Sb, and Cu.
2. The surface treated steel sheet of claim 1 , wherein the plated film is 1) a Zn plated film or 2) a plated film comprising Zn and an element having a higher ionization tendency than Zn.
3. The surface treated steel sheet of claim 2 , wherein the content of the element having a higher ionization tendency is in a range of 2 to 55 atom %.
4. The surface treated steel sheet of claim 1 , wherein the blackened film is 50 nm to 500 nm thick.
5. The surface treated steel sheet of claim 1 , wherein metal oxide particles precipitated in the blackened film have an average diameter ranging from 50 nm to 500 nm.
6. The surface treated steel sheet of claim 1 , further comprising a resin film on the organic and inorganic composite conversion coating film.
7. The surface treated steel sheet of claim 6 , wherein the resin film comprises one or more selected from the group consisting of polyurethane resin, polyacryl resin, epoxy resin, phenoxy resin, and polyester resin.
8. The surface treated steel sheet of claim 1 , wherein the organic and inorganic composite conversion coating film is composed of a conversion coating composition comprising 0.01 wt % to 0.2 wt % of phosphorous (P); 0.01 wt % to 0.2 wt % of magnesium (Mg); 0.005 wt % to 0.15 wt % of zirconium (Zr); 0.005 wt % to 0.15 wt % of titanium (Ti); 0.005 wt % to 0.15 wt % of vanadium (V); 0.05 wt % to 1 wt % of phenol resin; the balance of water, and other unavoidable impurities.
9. The surface treated steel sheet of claim 8 , wherein the conversion coating composition further comprising at least one of an antifoaming agent and a neutralizing agent to not more than 10 wt %.
10. The surface treated steel sheet of claim 8 , wherein the phenol resin comprises one or more functional group of halogen elements (F, Cl, Br, and I) or an amine group.
11. The surface treated steel sheet of claim 8 , wherein the phenol resin comprises one or more amine group selected from primary, secondary, tertiary and quaternary amine groups which are combined with one or more carbon atom, and one or more halogen element is combined at the middle or terminal of a polymer chain.
12. A method for manufacturing a surface treated steel sheet according to claim 5 comprising:
preparing a base steel sheet; forming a zinc or zinc alloy plated film on the base steel sheet;
forming a blackened film on the zinc or zinc alloy plated film; and
forming an organic and inorganic composite conversion coating film on the blackened film,
wherein the organic and inorganic composite conversion coating film is formed by a dipping or spraying method using a conversion coating composition including 0.01 wt % to 0.2 wt % of P; 0.01 wt % to 0.2 wt % of Mg; 0.005 wt % to 0.15 wt % of Zr; 0.005wt % to 0.15 wt % of Ti; 0.005 wt % to 0.15 wt % of V; 0.05 wt % to 1 wt % of phenol resin; 10 wt % or less of additives; and the balance of water.
13. The method of claim 12 , wherein the blackened film is formed by using a blackening solution comprising a metal ion, an organic acid, an inorganic acid ion, a surface modifier, and the balance of water.
14. The method of claim 13 , wherein the metal ion comprises 100 mmol/L to 1500 mmol/L one or more metal ion selected from the group consisting of Mg, Al, Zn, Fe, Ni, Co, Mn, and Ti, and 10 mmol/L to 50 mmol/L one or more selected from the group consisting of Sn, Sb, and Cu.
15. The method of claim 13 , wherein the organic acid comprises one or more selected from the group consisting of acetic acid, citric acid, tartaric acid, malic acid, oxalic acid, phthalic acid and maleic acid, and the content of the organic acid is in a range of 2-60 g/L.
16. The method of claim 13 , wherein the inorganic ion comprises one or more selected from the group consisting of NO 3 − , SO 4 2− , PO 4 3− , Cl − , ClO 3 − , and ClO 4 − such that pH of the blackening solution is in a range of 1.0 to 4.0.
17. The method of claim 13 , wherein the surface modifier comprises one or more selected from the group consisting of an amine complex agent, a polyamine complex agent, a polyol complex agent, polyalcohol complex agent, and an oxidizer.
18. The method of claim 12 , wherein the blackening solution has a pH range of 1.0 to 4.0.
19. The method of claim 12 , after the forming of the organic and inorganic composite conversion coating film, further forming a resin film on the organic and inorganic composite conversion coating film.