RC-428 Cyanide-Free Alkaline for Zinc Plating

INTRODUCTION

• Applied to both rack and barrel plating.

• It can produce a bright zinc coating over a wide range of current densities and temperatures, and also has excellent depth plating performance.

• The coating is easy to passivate.

• It has a low degree of brittleness and is especially suitable for some workpieces that require folding, forming, or welding after plating.

EQUIPMENT

Tank/Zinc dissolving tank: steel tank lined with hard rubber, and corrosion resistant materials such as reinforced PVC, PVC, PET, PE or PP.

Spare tank: 80-90℃ heat resistant material.

Anode: insoluble anode (flexible steel), the zinc metal content in the solution is replenished by the zinc dissolving tank. (Note: zinc anode and insoluble cannot be mixed).

Temperature: heating and cooling tubes require temperature-resistant and anti-corrosion materials, such as graphite, titanium, PTFE or steel etc.

Agitation: the stroke amplitude is 3-5 m/min when swept cathode and move horizontally.

Filtration: dust, dirt, carbonaceous powder, or grease in the bath will cause the coating to be rough, create pinholes or lack of gloss, so it is necessary to employ continuous cyclic filtration. The entire bath needs to be filtered 2-3 times within 1 hour, with the filter paper having a pore size below 10-20 mu. There must be no air in the filter pump, otherwise, very small bubbles will be created which will then form pinholes in the bath. The water intake of the filter pump must not be too close to the air tube to avoid inhaling air.

Ventilation: required.

FUNCTION OF THE COMPOSITION

Zinc oxide: the main source of zinc ions in the new make-up, which affects the plating performance and brightness.

Sodium hydroxide: a source of hydroxide in the solution, conductive salt, and an enhancement of throwing power.

REPLENISHMENT AND MAINTENANCE

MATTERS NEEDING ATTENTION

Sodium carbonate will form and accumulate in a cyanide-free alkaline bath. Sodium carbonate above 80 g/l will severely reduces the current efficiency of the bath, and freezing is recommended to remove crystallization of sodium carbonate.

Brighten the coating with 0.3-0.5 % nitric acid, which must be rinsed with sufficient water before it is passivated.

In barrel plating, the barrel must be fully immersed in the bath to avoid the hydrogen gas affecting the quality of the coating.

RC-428 Make-up and RC-428 Replenisher must be stored indoors in a  temperature range of 8-30. If the temperature is greater than 40 or less than 0, it will shorten the product’s life or solidify the additive.

COMPOSITION ANALYSIS

Ø Zinc metal

Reagents

Ammonia buffer: 55g of ammonia chloride, add 350ml of ammonium hydroxide, then 1 liter of pure water, mixed well.

Eriochrome black-T indicator

20 % formaldehyde solution

0.1M EDTA standard solution

Steps

1．Pipette a 2.0 ml sample, add 100 ml of pure water.

2．Add 10 ml of ammonia buffer.

3．Add 0.5 ml of Eriochrome black-T indicator

4．Add 10 ml of 20 % formaldehyde solution

5．Titration with 0.1M EDTA standard solution to blue end point.

Calculation: zinc metal (g/l) = 0.1M EDTA titration ml x 3.27

Ø Sodium hydroxide

Reagents

1 M barium chloride (244 g/l)

Potassium ferrocyanide solution (44 g/l)

Phenolphthalein indicator

1 M hydrochloric acid standard solution

Steps

1．Pipette a 5 ml of sample, add 100 ml pure water.

2．Add 20 ml 1 M barium chloride.

3．Add potassium ferrocyanide solution, the added ml is a 1/4 of the zinc metal in the bath. (e.g. if the zinc content of the metal is 24 g/l, the ml of the added potassium ferrocyanide solution is 6 ml).

4．Add 4 drops of phenolphthalein indicator.

5．Titration with 1 M hydrochloric acid standard solution to colorless end point.

Calculation: sodium hydroxide (g/l) = 1 M hydrochloric acid titration ml (a) x 8.0

Ø Sodium carbonate

Reagents

Potassium ferrocyanide solution (44 g/l)

Phenolphthalein indicator

1 M hydrochloric acid standard solution

Steps

1．Pipette a 5 ml of sample, add 100 ml pure water.

2．Add potassium ferrocyanide solution, the added ml is a 1/4 of the zinc metal in the bath.

3．Add 4 drops of phenolphthalein indicator.

4．Titration with 1 M hydrochloric acid standard solution to red disappear end point.

Calculation: Sodium carbonate (g/l) = [1 M hydrochloric acid titration ml- (a)] x 21.2

Note : (a) is the 1 M hydrochloric acid titration ml required to titrate sodium hydroxide

SAFETY AND ENVIRONMENTAL

A Material Safety Data Sheet (MSDS) includes product safety instructions and environmental protection instructions. Read and review the MSDS for appropriate health and safety warning before use.

WARRANTY

1. We provide guarantee for product quality under the valid law.

2. The quality of the product after reprocessing or repackaging by customer is not included in the guarantee.

3. Please feel free to contact us if you have any questions or issues about the products, we are ready to answer at any time.

COLOR & PACKAGING

RC-428 Make-up is colorless liquid with plastic barrel packaging. The packaging specification is 25 kg/pcs.

RC-428 Replenisher is light yellow liquid with plastic barrel packaging. The packaging specification is 25 kg/pcs.

?IMPORTANT NOTICE REGARDING THIS INSTRUCTION BOOK

The product information and recommendations contained in this document are based on our experimental theory and data. Due to the particularity of the surface processing, further as the actual use of our products by others is beyond our control, NO GUARANTEE of any kind is made as to the effects of such use, and NO RESPONSIBLE for any consequences. Also, all the information in this document cannot be used as evidence of copyright infringement.