Claims
- 1. A molten salt electroplating method for a steel member comprising:
- a step of drying a steel member which has been cleaned;
- a step of preheating said steel member;
- a step of activating said preheated steel member by anodic treatment in a molten salt solution; and
- a step of electroplating a metal by molten salt electroplating on the activated surface of said steel member
- the degree of oxidation of the surface of said steel member being detected during at least one of said drying step and said preheating step, and the anodic treatment conditions in said molten salt solution during said activation step being chosen in accordance with said detected degree of oxidation.
- 2. A molten salt electroplating method as claimed in claim 1, wherein said steel member is steel strip, or steel sheet, or steel wire, and electroplating is performed in a continuous manner.
- 3. A molten salt electroplating method as claimed in claim 1, wherein said salt is a chloride, and said metal which is electroplated is aluminum or an aluminum alloy.
- 4. A molten salt electroplating method as claimed in claim 1, wherein at least one of said drying step and said preheating step is performed in the atmosphere, and the maximum temperature which is reached by said steel member in said step which is performed in the atmosphere is given by the following formula when said maximum temperature is greater than 100.degree. C.:
- Tm .ltoreq. (44.4)logR + 120
- wherein
- Tm = maximum temperature reached by said steel member in the atmosphere (.degree.C.), and
- R = average rate of temperature increase of said steel member in the atmosphere during said drying step after cleaning and in said preheating step (.degree.C./sec).
- 5. A molten salt electroplating method as claimed in claim 1, wherein the degree of oxidation of said steel member is detected by measuring the surface temperature of said steel member or a temperature corresponding to said surface temperature.
- 6. A molten salt electroplating method as claimed in claim 1, wherein said preheating step is performed in an inert gas atmosphere, and said degree of oxidation is detected by measuring the surface temperature of said steel member just prior to said preheating step.
- 7. A molten salt electroplating method as claimed in claim 1, wherein said degree of oxidation is detected based on the maximum temperature of the surface of said steel member and the rate of temperature increase up to said maximum temperature in at least one of said drying step and said preheating step, said at least one step being performed in the atmosphere.
- 8. A molten salt electroplating method for as claimed in claim 1, wherein said steel member is selected from steel strip, steel sheet, and steel wire and said activating and electroplating steps comprise activating the surface of said steel member by anodic treatment followed by performing continuous molten salt electroplating of said steel member.
- 9. A molten salt electroplating method as claimed in claim 8, wherein said molten salt electroplating and said anodic treatment are performed in separate tanks.
- 10. A molten salt electroplating method as claimed in claim 8, wherein said steel member is plated with Al or an Al alloy, and said anodic treatment is performed using a molten salt solution comprising AlC1.sub.3 and a chloride of an alkali metal.
- 11. A molten salt electroplating method as claimed in claim 10, wherein a molten salt solution for said anodic treatment contains 50-54 mole % of AlCl.sub.3.
- 12. A molten salt electroplating method as claimed in claim 8, wherein said anodic treatment is performed using a counter electrode made of Al, Ti, or an alloy thereof.
- 13. A molten salt electroplating method as claimed in claim 8, wherein said anodic treatment is performed at a temperature which is at most 70.degree. C. above the melting point of a molten salt solution in which said anodic treatment is performed.
- 14. A molten salt electroplating method as claimed in claim 8, wherein a metal having a greater tendency to ionize than iron is added to a molten salt solution in which said anodic treatment is performed, and iron ions which are formed from said steel member during said anodic treatment are reduced and precipitate as elemental iron.
- 15. A molten salt electroplating method as claimed in claim 8, wherein after said molten salt electroplating, salt which adheres to the surface of said steel member is washed off by spraying the surface of said steel member with a solvent which has a boiling point which is lower than the temperature of said steel member immediately after said electroplating and which does not dissolve said salt, and after washing, said salt is separated from said solvent by gravity separation and recovered.
- 16. A molten salt electroplating method as claimed in claim 8, wherein exhaust gas from inside an electroplating tank used in said electroplating step is cooled in a cooler, and a mist or fume which is formed from the gaseous salt in said exhaust gas is recovered by a dust collector.
- 17. A molten salt electroplating method as claimed in claim 8, wherein exhaust gas from an electroplating tank used in said electroplating step is passed through a molten salt solution and gaseous salt in said exhaust gas is absorbed and recovered.
- 18. A molten salt electroplating method as claimed in claim 17, wherein said molten salt solution through which said exhaust gas from said electroplating tank is passed has the same composition as a molten salt solution which is used for said molten salt electroplating.
- 19. A molten salt electroplating method for a steel member comprising:
- a step of drying a steel member which has been cleaned;
- a step of preheating said steel member;
- a step of activating said preheated steel member by anodic treatment in a molten salt solution;
- a step of electroplating a metal by molten salt electroplating on the activated surface of said steel member; and
- a metal having a greater tendency to ionize than iron being added to a molten salt solution in which said anodic treatment is performed, and iron ions which are formed from said steel member during said anodic treatment being reduced and precipitated as elemental iron.
- 20. A molten salt electroplating method as claimed in claim 19, wherein said metal comprises aluminum powder which is added to said molten salt solution in which said anodic treatment is performed.
- 21. A molten salt electroplating method as claimed in claim 20, further comprising a step of separating said elemental iron from said molten salt solution in which said anodic treatment is performed.
- 22. A molten salt electroplating method as claimed in claim 19, wherein said aluminum powder is provided as a packed layer and said molten salt solution in which said anodic treatment is performed is passed into contact with said packed layer.
- 23. A molten salt electroplating method for a steel member comprising:
- a step of drying a steel member which has been cleaned;
- a step of preheating said steel member;
- a step of activating said preheated steel member by anodic treatment in a molten salt solution;
- a step of electroplating a metal by molten salt electroplating on the activated surface of said steel member; and
- after said molten salt electroplating, a step of washing off salt which adheres to the surface of said steel member by spraying the surface of said steel member with a solvent which has a boiling point which is lower than the temperature of said steel member immediately after said electroplating and which does not dissolve said salt, and after washing, said salt being separated from said solvent by gravity separation and recovered.
- 24. A molten salt electroplating method as claimed in claim 23, further comprising a step of returning said salt separated from said solvent by gravity separation to said molten salt in which said electroplating step is performed.
- 25. A molten salt electroplating method for a steel member comprising:
- a step of drying a steel member which has been cleaned;
- a step of preheating said steel;
- a step of activating said preheated steel member by anodic treatment in a molten salt solution;
- a step of electroplating a metal by molten salt electroplating on the activated surface of said steel member; and
- exhaust gas from inside an electroplating tank used in said electroplating step being cooled in a cooler, and a mist or fume which is formed from the gaseous salt in said exhaust gas being recovered by a dust collector.
- 26. A molten salt electroplating method as claimed in claim 25, wherein said inside of said electroplating tank is maintained at a negative pressure.
- 27. A molten salt electroplating method for a steel member comprising:
- a step of drying a steel member which has been cleaned;
- a step of preheating said steel member;
- a step of activating said preheated steel member by anodic treatment in a molten salt solution;
- a step of electroplating a metal by molten salt electroplating on the activated surface of said steel member; and
- exhaust gas from an electroplating tank used in said electroplating step being passed through a molten salt solution and gaseous salt in said exhaust gas being absorbed and recovered.
- 28. A molten salt electroplating method as claimed in claim 27, wherein said molten salt solution through which said exhaust gas from said electroplating tank is passed has the same composition as a molten salt solution which is used for said molten salt electroplating.
- 29. A molten salt electroplating method as claimed in claim 27, further comprising a step of adding said molten salt solution through which said exhaust gas from said electroplating tank is passed to said molten salt used in said electroplating step.
Parent Case Info
This application is a divisional, of application Ser. No. 202,048, filed June 3, 1988.
US Referenced Citations (4)
Foreign Referenced Citations (2)
Number |
Date |
Country |
1300414 |
Jul 1969 |
DEX |
1300415 |
Jul 1969 |
DEX |
Non-Patent Literature Citations (1)
Entry |
Nayak et al., "The Electrodeposition of Aluminum on Mild Steel From a Molten Aluminum Chloride-Sodium Choloride Bath", Journal of Applied Electrochemistry 9 (1979), 699-706. |
Divisions (1)
|
Number |
Date |
Country |
Parent |
202048 |
Jun 1988 |
|