There is nowhere...
You have to poke yourself.
It's not hard.
I plan to dip nickel plating, without electricity.
Chemical nickel plating
April 29, 2014 galwanizernie.pl Galvanic processes
Chemical nickel plating is a valuable supplement to galvanic nickel plating, mainly in the field of technical and anti-corrosion coatings and where electrolytic nickel plating fails, e.g. when plating highly profiled products with tight dimensional tolerances.
Chemical nickel coatings can be deposited by exchange, contact and catalytic processes, but only the latter method has found application in industrial practice.
In the catalytic nickel plating process, the nickel coating is deposited on the catalyst surface as a result of the reduction of nickel ions with hydrogen in statu nascendi in baths containing reducing substances. In this process, it is important that the reduction catalyst is not only the metal to be coated, but also the metal to be deposited, which allows the deposition of coatings of the desired thickness.
Two types of chemical nickel plating baths are currently used:
• alkaline operating in the pH range of 8-10
• acidic ones operating at pH 4–6
The basic components of chemical nickel baths are nickel salts and a reducing agent, mainly sodium hypophosphite. In addition, the bath contains complexing and buffering compounds as well as inhibitors whose task is to prevent spontaneous decomposition of the bath and counteract rapid changes in pH.
The reactions occurring in the chemical nickel plating process can be represented as follows:
• NiSO4 + 2 NaH2PO2 + 2 H2O → Ni + 2 NaH2PO3 + H2SO4 + H2
• NaH2PO2 + H → P + H2O + NaOH
In reaction 1, sodium hypophosphite reduces the nickel ion to metallic nickel. In reaction 2, hypophosphite is reduced with release of free phosphorus, which forms a solid solution with nickel.
Chemical nickel coatings contain 7 to 15% phosphorus and can be applied directly to steel, iron, nickel, cobalt, and aluminum and its alloys. Coating of other metals that are not reduction catalysts, such as copper and brass, is done by short-term contact of the metal being coated with the catalysing metal. After the formation of the first nickel nuclei on the surface, the reaction proceeds spontaneously on the principle of autocatalysis.
In the development of chemical nickel plating technology, three types of baths can be distinguished.
The first one is a bath with limited durability and low rate of coating deposition. When the nickel content in the bath drops to 50%, its exploitation becomes unprofitable. This results in a waste of 50% of the ingredients and increased costs of wastewater neutralization.
The second type are catalytic baths known as Kanigen (Cataltic Nickel Generation). These baths enable coatings to be deposited at a satisfactory rate and can be regenerated many times, which allows the use of up to 30 g of nickel from 1 l of the bath. The disadvantage of the process is that it is safer to regenerate the bath at ambient temperature or approx. 30°C lower than the working temperature. Despite this drawback, these baths are widely used in industry due to their high durability.
The third type are catalytic baths with the possibility of refilling them at operating temperature. Thanks to the use of a combination of 2 different complexing compounds and supplementing the pH with ammonium hydroxide or potassium carbonate, it is possible to reduce the operating temperature of the bath to 85°C while maintaining durability and efficiency.. These properties of the bath together with the simplification of the technological process determine their increasingly wide industrial application.
Bath compositions for chemical nickel plating
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###Alkaline baths
A typical alkaline bath has the following composition:
Nickel chloride NiCl2.6H2O 30 g/l
Sodium hypophosphite NaH2PO2 20 g/l
Sodium citrate Na3C6H5O7.2H2O 50 g/l
Ammonium chloride NH4Cl 15 g/l
Working conditions:
Temperature 40-85°C
pH 8.8-9.5
Bath load 0.6-1.0 dm²/l
Alkaline baths are less durable than acid baths and more sensitive to contamination. The rate of coating deposition is approx. 10µm/hour, and intensive hydrogen evolution causes porosity of the coatings. In addition, these baths are less economical due to the large losses of ammonia, which is used to supplement the pH.
The advantage of alkaline baths is easy pH control. Baths with a pH range of 8.8 - 10 have a blue color, at a lower pH value they become green.
Despite the above reservations, alkaline baths are used with good results for the nickel plating of some non-ferrous metals, e.g. titanium, as well as other materials such as silicon, silicon and titanium ceramics and plastics.
### Acid baths
Acid baths are stable, characterized by a deposition rate in the range of 15 - 20 µm/hour and have been used for applying nickel coatings on most metals, especially steel.
A typical acid bath for chemical nickel plating has the following composition:
Nickel sulfate NiSO4.7H2O 25 g/l
Sodium hypophosphite NaH2PO2.H2O 30 g/l
Lactic acid C3H6O3 35 ml/l
Sodium hydroxide NaOH 10 g/l
Stabilizing additives 15 ml/l
Working conditions:
Temperature 85-95°C
pH 4.4-4.6
Bath load 0.6-1.0 dm²/l
Periodic filtration
The rate of deposition of the nickel coating, defined as the ratio of the thickness of the coating to the time of its deposition, depends primarily on the pH and temperature of the bath. It was found that the deposition rate of the nickel coating increases with increasing pH and bath temperature and reaches the highest value at a temperature close to the boiling point. It should be noted, however, that exceeding the permissible values of these parameters may lead, if not to bath decomposition, to the formation of decomposition nuclei causing coating roughness.
Therefore, in order for the amount of nickel-plated surface obtained from a bath volume unit until its replacement, defined as the "bath life time", to be as large as possible, not only the working conditions, but also guidelines regarding bath cleanliness and the method of its maintenance and replenishment should be observed.
The reaction describing the process of chemical nickel plating shows that to deposit 1 gram atom of nickel, the following are consumed:
• 1 gram of nickel sulphate
• 3 grams of sodium hypophosphite
• 1 gram of sodium hydroxide to neutralize the acid formed in the reaction
These compounds are the basic components of regeneration solutions. These solutions also contain other components of the bath in the amount corresponding to the losses due to wear, decomposition and carrying away. Regeneration of the bath consists in supplementing it, according to the results of the nickel analysis, with regeneration solutions in an equal volume.
Bath maintenance consists of:
• periodic bath filtration to remove impurities,
• checking the bath level and refilling it to the initial volume,
• determining the pH of the bath and, if necessary, supplementing it with a 20% NaOH solution with intensive mixing,
• regeneration of the bath according to the results of the analysis,
• testing the rate of coating deposition. Steel samples with an area of 15 cm2, pre-degreased and pickled, are nickel-plated in a bath for 1 hour, and then the thickness of the applied coating is measured. It should be, depending on the amount of regeneration, from 10 to 20µm.
Properties of chemical nickel coatings
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Chemical nickel coatings are characterized by the same thickness on all surfaces of the coated object. With a properly conducted process, the spread of the coating thickness is 0.5 µm.
The coatings contain from 7 to 15% of phosphorus and immediately after application they show an amorphous structure, which changes after heat treatment with the precipitation of nickel phosphide. Changing the structure entails an increase in hardness and wear resistance. Depending on the time and temperature of heat treatment, chemical nickel coatings are obtained with hardness and wear resistance corresponding to technical chrome coatings.
A characteristic feature of chemical nickel coatings is high corrosion resistance. These coatings are completely resistant to organic acids, alcohols, aldehydes and esters, they also show high resistance to sea water and distilled water. High corrosion resistance is associated with low porosity of coatings deposited from an acid bath. Tests have shown that coatings with a thickness of more than 15µm are completely tight. It was assumed that for severe corrosion conditions, the thickness of chemical nickel coatings should be 25 - 30µm.
Chemical nickel coatings should not be applied to products exposed to solutions of ammonium salts, nitric and acetic acids.
(found on the web)
adam m
. Conspiracies are everywhere, from Smolensk to Brussels. Didn't you know about it? And in fact, it's a hopeless battery in the sense of high internal resistance. Therefore, it has long been supplanted by other types of batteries. The last time I saw such a battery was in a pre-war mining lamp, years ago. Making it at home is practically impossible, because where will you get sponge nickel plates pressed with nickel hydroxide? And how do you make spongy iron slabs at home? The only thing I like about these batteries is their indestructibility.
