PROCESS AND DEVICE FOR CLEANING GALVANIC BATHS TO PLATE METALS
The invention concerns a process which is used to plate functional layers of acidic or alkaline zinc or zinc alloy baths which contain nitrogenous organic additives, a soluble zinc salt and if necessary other metal salts selected from Fe, Ni, Co and Sn salts, where the bath composition for the regeneration is conveyed through an appropriate device having an ion exchanger resin to remove cyanide ions.
1 . Process used to deposit functional layers of zinc or zinc alloys from alkaline zinc or zinc alloy plating baths which contain nitrogenous organic additives, a soluble zinc salt and optionally other metal salts, comprising the following steps:
(i) providing a zinc or zinc alloy bath containing the above mentioned components;
(ii) electrolytically depositing a zinc or zinc alloy layer on a substrate that is to be coated according to known processes;
(iii) removing at least a part of the zinc or zinc alloy bath and conveyancing the part that has been removed and which contains cyanide ions and nitriles that have been formed during the deposition according to step (ii) through a device that includes an ion exchange resin which is designed specifically for separating cyanide ions;
(iv) returning the conveyed part to the zinc or zinc alloy bath.
2 . Process according to claim 1 , characterised in that the other metal salts are selected from the group consisting of Fe, Ni, Co and Sn salts.
3 . Process according to claim 1 , characterised in that the following procedural step is also scheduled:
(v) Supplementing of used components from the zinc or zinc alloy bath.
4 . Process according to claim 1 , characterised in that the removal of the part of the zinc or zinc alloy bath and its return is a continuous or discontinuous process.
5 . Process according to claim 1 , characterised in that the zinc or zinc alloy bath contains organic additives selected from brighteners, surface-active agents and nitrogenous complexing agents.
6 . Process according to claim 1 , characterised in that the nitrogenous complexing agents are selected from the group comprising polyalkyleneamines.
7 . Process according to claim 1 , characterised in that it is a galvanic bath which is used to plate zinc-nickel alloys.
8 . Process according to claim 1 , characterised in that the ion exchange resin is selected from the group consisting of strongly alkaline anion exchange resins.
9 . Process according to claim 1 , characterised in that the ion exchange resin is selected from the group consisting of ion exchange resins having as a functional group quaternary amines.
10 . Process according to claim 1 , characterised in that the ion exchange resin is regenerated through contact with a sodium chloride solution and then by means of conditioning using sodium hydroxide.
11 . Process according to claim 10 , characterised in that the sodium chloride solution presents a sodium chloride concentration of 5-35% by weight.
12 . Process according to claim 10 , characterised in that the temperature of the sodium chloride solution is 10-70° C. during regeneration on the ion exchanger column.
13 . Process according to claim 1 , characterised in that the process includes the additional step iii b) cooling of the zinc or zinc alloy bath for the separation of sodium carbonate at a temperature which is below 10° C.
14 . Device used to carry out the process according to claim 1 , comprising a receptacle to take a zinc or zinc alloy bath, a connected pump system, which is connected to the ion exchanger device to take the zinc or zinc alloy bath, which has an ion exchanger and a collection device for the zinc or zinc alloy bath conveyed through the ion exchanger resin, which is identical to the receptacle.
15 . Device according to claim 14 , characterised in that the ion exchanger resin in the ion exchanger device is on a spray register, spray pole or sieve.
16 . Device according to claim 14 , characterised in that there is a freezing device between the receptacle and the ion exchanger device to cool the solution and separate a sodium carbonate solid.
17 . Process according to claim 11 , characterised in that the temperature of the sodium chloride solution is 10-70° C. during regeneration on the ion exchanger column.
18 . Device according to claim 15 , characterised in that there is a freezing device between the receptacle and the ion exchanger device to cool the solution and separate a sodium carbonate solid.