NON-CYANIDE ZINC NICKEL PROCESS

Transcription

1 NON-CYANIDE ZINC NICKEL PROCESS PHYSICAL PROPERTIES: ZINNI AL 451: Dark-blue liquid ZINNI AL 452: Transparent violet liquid ZINNI AL 453: Transparent yellowish liquid DESCRIPTION: The process is an alkaline non-cyanide zinc nickel plating system for rack and barrel plating. produces bright zinc nickel deposits over the total current density and temperature ranges up to 30 C with % nickel. It has a excellent covering, throwing power and metal distribution. Zinc nickel plated parts can easily be chromated transparent, black and yellow, resulting in an excellent corrosion resistance. OPERATING INSTRUCTIONS: Cathode current density: Anode current density: Voltage: Up to 4 A/dm² for rack plating with agitation Up to 1.5 A/dm² for barrel plating Up to 2 A/dm² 6 18 Volts Temperature: C Efficiency: Anodes: %, depending on zinc content and current density. Nickel anodes or nickel plated steel Zinc solution: In a separate tank; % zinc DIN 1706 Anode to cathode ratio: 1:1 2:1 Deposition rate: 0.35 µm/min at 2 A/dm² Analysis Values: Rack Barrel Zn metal 7 11 g/l 7 11 g/l Nickel g/l g/l NaOH g/l g/l H. Donsbach Rev /5

2 EQUIPMENT: Tanks: Exhaust: Filtration: Agitation: Steel - rubber or PVC lined. Is recommended. To avoid roughness of deposits, continuous filtration is recommended. Bath turnover of 2 3 times per hour. Cathode agitation of 2 5 m/min. Low air agitation is also possible. Barrel rotation should be 3 5 rpm. MAKE-UP FOR 100 LITRE PLATING SOLUTION: Rack/Barrel Zinc oxide NaOH Nickel Solution ZINNI AL 451: Basic Brightener ZINNI AL 452: Brightening Agent ZINNI AL 453: 1.2 kg 12.0 kg l l l Dissolve caustic soda in one fifth of the required amount of water, if possible deionised water. Then add zinc oxide, stir well, and dissolve. Allow to cool down to room temperature and add up with water to 85 %, then add the required amount of additives. Please note that ZINNI AL 451 and 452 must be always mixed together before adding to the bath. Fill the bath up to desired volume with water. It is suggested to electrolyse the solution for several hours at normal current densities before starting regular plating. MAINTENANCE: We recommend to make frequent, small additions of all additives to insure constantly good results. If brightness of the work falls off rapidly, it is recommended to make a chemical analysis of the plating solution and bring the bath back to normal conditions before making any large additions of additives. The additives cannot compensate improperly balanced plating solutions. H. Donsbach Rev /5

3 Consumption per 10,000 A/h: Nickel Solution ZINNI AL 451: Basic Brightener ZINNI AL 452: Brightening Agent ZINNI AL 453: Rack/Barrel l l depending on drag-out and concentration of carbonate l GENERAL INFORMATION: Zinc: The zinc has to be dissolved in a separate tank by using zinc anodes % in iron or nickel plated iron baskets. The zinc solution will be added to the bath using a filter pump. Sodium carbonate: The sodium carbonate content should be under 80 g/l. Nickel: The content of nickel in the electrolyte will be adjusted by the Nickel Solution ZINNI AL 451. As the percentage of nickel in the deposit is approx % per 1 kg zinc, approx kg nickel will be plated. This amount of nickel is dissolved in 1.3 l Nickel Solution ZINNI AL 451. It is recommended to control the nickel content in the electrolyte as well as in the deposit (AAS, X-Ray). For a good chromate ability and corrosion resistance it is important to maintain the nickel content in the deposit between %. The following parameters influence the nickel content in the deposit: - The ratio Ni : Zn in the electrolyte. - Higher content of nickel in the electrolyte increases the content of nickel in the deposit. - Higher content of zinc in the electrolyte decreases the content of nickel in the deposit. - All parameters which decrease the current efficiency for the zinc plating increase the percentage of nickel in the deposit. These are: H. Donsbach Rev /5

4 - Lower zinc content. - High carbonate content. - Too low temperature. - High current density. - Overloaded on ZINNI AL 452 and/or ZINNI AL Weak agitation. At a current density of 1 A/dm² and 100 % current efficiency approx microns zinc nickel will be deposited per minute. The electrolyte will be controlled by analysis and in hull cell. HULL CELL TEST: With magnetic stirrer or air agitation. Current density: Time: 1.0 A minutes POST - TREATMENT: After activation in 0.1 Vol.% hydrochloric acid parts will be chromated in special black, clear or yellow chromates. BARREL PLATING: The zinc nickel plating in barrel requires special measures, because in this case additional parameters influence the plating and the chromate ability. These are: - Barrel movement. - Barrel filling. - Exchange of the electrolyte in the barrel. H. Donsbach Rev /5

5 - The current conditions during plating etc. For that reason an optimum plating has to be adjusted at each plant. The data for rack plating cannot be used for barrel plating. SAFETY PRECAUTIONS: See Material Safety Data Sheets GUARANTEE: Above instructions and recommendations are the result of intensive testing and shop experiences. They are for your information, only. Our guarantee extends to the continuous quality of our products as they leave our factory and not to their usage in the field, which is a factor beyond the control of a supplier. H. Donsbach Rev /5