Phosphate solution for zinc or zinc-based alloy plated steel sheet, and zinc or zinc-based alloy plated steel sheet using the same
A phosphate solution for a zinc or zinc-based alloy plated steel sheet, and a zinc or zinc-based alloy plated steel sheet using the same are provided. The phosphate solution for a zinc or zinc-based alloy plated steel sheet contains a molybdenum (Mo) ion, a calcium (Ca) ion and a phosphate ion. A zinc or zinc-based alloy plated steel sheet includes a base steel sheet, a zinc-based or zinc alloy-based plating layer formed on the base steel sheet, and a phosphate film formed on the zinc-based or zinc alloy-based plating layer. The phosphate film contains a molybdenum compound, Ca and a phosphate. A pitting phenomenon occurring at the time of treating a steel sheet with a phosphate is prevented, and excellent corrosion resistance is exhibited on a phosphate film.
1. A zinc or zinc-based alloy plated steel sheet comprising:
a base steel sheet;
a zinc-based or zinc alloy-based plating layer formed on the base steel sheet; and
a phosphate film formed on the zinc-based or zinc alloy-based plating layer,
wherein the phosphate film contains a molybdenum compound, calcium (Ca) and a phosphate, and
wherein the Ca and the phosphate are present as a scholzite film.
2. The zinc or zinc-based alloy plated steel sheet of claim 1 , wherein the zinc-based or zinc alloy-based plating layer is a Zn—Mg-based plating layer.
3. The zinc or zinc-based alloy plated steel sheet of claim 2 , wherein the Mg is contained in an amount of 3 to 30 wt %.
4. The zinc or zinc-based alloy plated steel sheet of claim 1 , wherein the zinc-based or zinc alloy-based plating layer is formed using a dry plating process.
5. The zinc or zinc-based alloy plated steel sheet of claim 1 , wherein the molybdenum compound is MoO3.
6. The zinc or zinc-based alloy plated steel sheet of claim 1 , wherein the scholzite film contains magnesium (Mg).
7. The zinc or zinc-based alloy plated steel sheet of claim 1 , wherein the phosphate film is adhered in a range of 1 to 5 g/m2, and an average size of crystalline grains is in a range of 1 to 10 μm.
8. The zinc or zinc-based alloy plated steel sheet of claim 1 , wherein the phosphate film additionally contains Zn and Mn.
9. The zinc or zinc-based alloy plated steel sheet of claim 1 , wherein the phosphate film additionally contains Ni.