Acid Zinc Process Unizinc Acz 540
ACID ZINC PROCESS UNIZINC ACZ 540
PHYSICAL PROPERTIES:UNIZINC ACZ 542: Brown Liquid.
UNIZINC ACZ 544: Brown Liquid.
DESCRIPTION:
The UNIZINC ACZ 540 process uses a water-soluble, single brightener system and produces full bright to brilliant, ductile zinc deposits from an ammoniated- or non- ammoniated chloride based acid zinc solution.
A conversion from one type to the other can be done by simply exchanging the previously used ammonium chloride with potassium chloride. It exhibits excellent covering power, can be used over a wide range of zinc metal contents and is therefore well suited for both rack and barrel plating.
UNIZINC ACZ 540 produces extremely bright, chromelike deposits which shows a marked degree of levelling, not generally experienced in zinc plating.
UNIZINC ACZ 540 has low power requirements, lower than alkaline or cyanide solutions and produces zinc deposits which can easily be blue-, yellow-, olive- or black-chromated.
EQUIPMENT:
Plating tanks should be lined with an acid resistant plastic coating. Anodes must be
99.9 % pure zinc. For still operation, cathode agitation is recommended. Heating, and filtration facilities should be available.
OPERATING INSTRUCTIONS:
Current:
Cathode current density0,2 - 8,0 A/dm²
Anode current density0,5 - 3,0 A/dm²
Voltage: 3 - 8 volts
Temperature: 15 - 50° C
Cathode Efficiency: 85 - 95 %
pH-Value:4.6 - 5.8
BATH COMPOSITIONS:
AMMONIA-BATH:
CHEMICALSBARRELRACK
Zinc chloride 40 g/l 80 g/l
Ammonium chloride180 g/l150 g/l
pH-value4.6 - 5.84.6 - 5.8
Above plating solutions are typical ammonia solutions, which can be changed according to each requirement.
Initial addition:
UNIZINC ACZ 54230 - 40 ml/l
UNIZINC ACZ 544 2 - 4 ml/l
POTASSIUM-BATH:
CHEMICALSBARRELRACK
Zinc chloride 50 g/l 80 g/l
Potassium chloride180 g/l200 g/l
Boric acid 25 g/l 25 g/l
pH-value4.6 - 5.84.6 - 5.8
Above plating solutions are typical potassium solutions, which can be changed according to each requirement.
Initial addition:
UNIZINC ACZ 54220 - 30 ml/l
UNIZINC ACZ 544 1 - 3 ml/l
MAKE UP OF A PLATING SOLUTION:
Chemicals should be dissolved in 1/2 the required amount of warm, de-ionized water. After filling up with cold water and filtration, pH should be adjusted and required amounts of UNIZINC ACZ 542 andUNIZINC ACZ 544 should be added.
It is important that UNIZINC ACZ 542 be added first, stirred well, then
UNIZINC ACZ 544.
CONSUMPTION PER 10.000 Ah:
UNIZINC ACZ 5420,5 - 0,8 l
UNIZINC ACZ 5441,0 - 2,0 l
UNIZINC ACZ 544 contains the brightener and the proper proportion of wetting agent for normal maintenance. Should, however, part of the wetting agent be emulgated or soponified, it might be necessary to add UNIZINC ACZ 542. The required amount of UNIZINC ACZ 542 can be determined by running Hull Cell Panels or by running a stalogmometer test.
If the cloudypoint can not be kept above the working temperature by adding
UNIZINC ACZ 542, what is usually not necessary, the separate additions of our special Addition Agent ZN - 543 is recommended.
GENERAL INFORMATION:
Since Acid Zinc Processes in general have no inherent cleaning power like those of cyanide solutions, it is very important that work to be plated enters the plating tanks thoroughly clean. The pH-value should be checked electrometically at least once every four working hours.
Parts, which may have fallen into the plating tank, should be taken out immediately, to avoid iron contamination. Dark brown spotting or barrel perforation marks are indications of iron contamination. Iron can be taken out, by adding small amounts of Hydrogen peroxide to the plating solution, which should have a pH of not less than 5.8. Precipitated iron should be filtered out of the plating solution in order to avoid roughness of the deposit.
NOTE:
In barrel plating, solution drag-out losses are sometimes high. We recommend to replenish UNIZINC ACZ 542 by calculating the loss of chloride in % and adding the equivalent amount of UNIZINC ACZ 542 to the solution.
EXAMPLE:
Normal chloride content:120 g/l
Chloride content per analysis:100 g/l
% Loss of Chloride:16.7 %
______
Normal UNIZINC ACZ 542 content:40 ml/l
% Loss of UNIZINC ACZ 542:16.7 %
ml UNIZINC ACZ 542 lost:6,7 ml/l
INFLUENCE OF PLATING SOLUTION PARAMETERS:
The following statements are not necessarily true for all installations. Parameters can vary and are interdependent on each other. These statements should be considered as guidlines, only, whenever problems occur.
- zinc metal concentration too high:
This can be the reason for a poor metal thickness distribution.
- zinc metal concentration too low:
This can be the reason for HCD burning.
- chloride concentration too high:
This can lead to dissolving of metal (zinc and/or basic metal). It can also cause some brittleness.
- chloride concentration too low:
This can lead to reduction in zinc metal content and a slight burn in the HCD area.
- boric acid (or ammonium-) concentration too high:
This can be the reason for grey deposits and roughness at the HCD area.
- boric acid too low:
This can lead to rough deposits, since a lack of boric acid causes a loss of the buffer effect in the diffusion layer during deposition.
- pH value too high (above 5.8)
This can lead to buring at the HCD, a loss of zinc metal concentration and formation of metalhydroxides.
- pH value too low (below 4.6)
This can lead to an increase in metallic impurities (dissolving of basis metal), a decrease in covering power and metal distribution.
SAFETY PRECAUTIONS:
UNIZINC ACZ 540 additives and plating solutions are poisonous.
Necessary safety precautions should be adhered at all times.
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 useage in the field, which is a factor beyond the control of a supplier.
H.DonsbachRev 1.115.11.20021/4