Determination of Zinc concentration in Acid Zinc, Alkaline Zinc and Zinc-Nickel plating baths

Zinc analysis is a fundamental control in acid, alkaline, and Zinc-Nickel plating baths, as it allows the chemical composition to be maintained within the optimal process parameters. Zinc concentration directly affects deposition rate, current efficiency, and coating uniformity. In acid and alkaline baths, maintaining the correct zinc level helps ensure process stability, aesthetic quality, and uniformity of the deposited thickness. In Zinc-Nickel baths, zinc control is particularly important for maintaining the correct balance between zinc and nickel and obtaining an alloy with consistent characteristics. A non-optimal value may in fact compromise the appearance, adhesion, and corrosion resistance of the coating. Regular analysis makes it possible to promptly detect any variations in bath composition and carry out the necessary corrections. Rapid control directly on the production line also helps reduce intervention times and prevent defects in treated parts. Zinc monitoring therefore contributes to reducing rejects and chemical consumption. In all three processes, it is therefore an essential parameter for ensuring stability, repeatability, and high-quality zinc plating.

Method

Test type: End Point.

Testing time: 1 minute.

Analysis sessions with multiple samples are possible up to a maximum of 16 tests for CDR GalvanLab^® and 3 tests for CDR GalvanLab^® Junior.

Step 1/16

Place the test tubes containing reagent R1 in one of the incubation cells and let them warm for at least 10 minutes.

Step 2/16

Dilute the sample to 1:20. Dilute by adding 50 ul of sample to the dilution cuvette (code *400345). The proper working procedure is described in the following slides.

Step 3/16

Collect 50 µL of sample with a pipette. Use a new tip for each test to prevent contamination from previous samples.

Step 4/16

Carefully clean the outside of the pipette tip with blotting paper, avoiding contact between the extremity of the tip and the paper.

Step 5/16

Place the sample in the dilution cuvette. Keeping the tip immersed in reagent, press and release the piston of the pipette several times.

Step 6/16

Gently shake the cuvette 2-3 times.

Step 7/16

Collect 10 µL of diluted sample with a pipette. Use a new tip for each test to prevent contamination from previous samples.

Step 8/16

Carefully clean the outside of the pipette tip with blotting paper, avoiding contact between the extremity of the tip and the paper.

Step 9/16

Place the sample in the cuvette. Keeping the tip immersed in reagent, press and release the piston of the pipette several times.

Step 10/16

Gently shake the cuvette 2-3 times.

Step 11/16

Place the cuvette in one of the incubation cells and start the timer by pressing the timer icon.

Step 12/16

Select the cuvette to be read from the display. Place the cuvette in the cell marked with the blue light and press READ.

Step 13/16

Collect 30 µL of R2 with the pipette.

Step 14/16

Carefully clean the outside of the pipette tip with blotting paper, avoiding contact between the extremity of the tip and the paper.

Step 15/16

Add 30 µL of R2 to the cuvette without touching the tip in the liquid. In case of contamination, replace the tip.

Step 16/16

Place the cuvette in the cell marked with the blue light and press READ to perform the photometric reading.

Sample treatment

Dilute the sample using the included dilution kit, as specified in the method, according to the sample volume indicated in the table for each analysis. The Zinc-Nickel [5.0–30.0]g/L method also requires filtration of the sample.

Principle of the test

The zinc content is determined by its reaction with a specific chromogen, which develops a color in the presence of this metal. The color intensity, measured at 578 nm, is proportional to the Zn concentration in the sample. The use of a selective dilution kit allows zinc to be determined in acidic zinc, alkaline zinc, and zinc-nickel baths.

Calibration curve

The calibration curve of the CDR method for zinc determination was obtained by correlation with the results obtained using the ICP reference method.

Reagent test Kits

Code *400330: 100 test
Code *400335: 10 test
The reagents have a shelf-life of 6 months

To be used with the dilution kits:
Acid Zinc:
Code *400340: 100 test
Code *400345: 10 test
Alkaline Zinc:
Code *400360: 100 test
Code *400365: 10 test
Zinc-Nickel:
Code *400350: 100 test
Code *400355: 10 test
The dilutions have a shelf-life of 6 months

Measuring range

Analyses	Measuring range	Resolution	Repeatability
Acid Zinc [10-50] g/L	10 - 50 g/L	0.1 g/L	0.6 g/L
Alkaline Zinc [5-30] g/L	5 - 30 g/L	0.1 g/L	0.3 g/L
Zinc in ZnNi bath [5-30] g/L	5 - 30 g/L	0.1 g/L	0.3 g/L

The chemical analysis instruments for electroplating baths

CDR GalvanLab®

Complete analysis panel, supplied already configured
Up to 16 determinations simultaneously
Possibility of carrying out analyses of the same sample
Integrated printer
Full connections (LAN - USB - Bluetooth barcode/QR code reader)

CDR GalvanLab® Jr

Partial analysis panel, customisable configuration
Up to 3 determinations simultaneously
Wireless connection to external printer
USB connections

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