Determination of phosphorus in the hottest electro

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Determination of phosphorus in electroless nickel plating deposits

the term "electroless plating process" is used to describe the method of electroplating by chemical reduction. Electroless nickel plating is carried out by reducing nickel ions in a solution containing phosphite, boron or hydrazine compounds. Electroless nickel deposit is not pure nickel, which contains a lot of phosphorus. The content of phosphorus can vary with strength, ductility, stress, magnetism and structure, usually between%. The phosphorus content in the sediment is greatly affected by the pH value of the bath; Phosphorus content increases with the decrease of pH value. The sediment produced by the commonly used acid bath contains about% phosphorus. An increase in hypophosphite concentration will result in an increase in the phosphorus content of the bath sediment at a given pH. The phosphorus content of sediment is affected by bath temperature. Heating treatment at 400 ℃ will lead to the growth of precipitated intermetallic Ni3P phase and particles. The precipitate containing about 7% phosphorus by weight consists of 50% Ni3P and 50% nickel by volume. The sediment with low phosphorus content is composed of Ni3P in the nickel matrix, while the sediment with high phosphorus content is on the contrary. Using a lower pH solution to obtain a higher phosphorus content and a higher ratio between phosphate and nickel ions will result in high strength and low stress. The alloy is a supersaturated solid solution of nickel phosphide in nickel. [1]

due to the need of manufacturing and the fact that it is impossible to determine 7%-13% phosphorus in electroless nickel plating deposits by EDS (energy dispersive spectroscopy), chemical methods are used to check the phosphorus in electroless nickel plating deposits. Phosphorus can be analyzed through two common processes: using appropriate chemical methods to convert phosphorus into dissolved orthophosphate and determine the dissolved orthophosphate. In order to determine the phosphorus in the precipitate of electroless nickel plating, gravimetric analysis and photometric experiments have been carried out

in the gravimetric method, the determined phosphorus heteropolyphosphate molybdate (NH4) 3h4[p (mo2o7) 6] is precipitated, cleaned, dried and weighed

the gravimetric method for determining the phosphorus content in different samples (such as steel and cast iron) is very accurate, and more than one method is usually used to check the determined substances [2,3]

method summary

dissolve the sediment in nitric acid and oxidize it with potassium permanganate under acidic conditions. Ammonium molybdate was added and reacted with phosphorus (V) to form a yellow precipitate of heteropolyphosphate (NH4) 3h4[p (mo2o7) 6]


reagents and instruments:

all materials are reagent grade, and there is no further purification during use

prepare all solutions with distilled water. Store the solution in glass bottles and polyethylene bottles. Use deionized water (micro Siemens) standard solution of phosphorus (1 ml = 1.0 mg phosphorus)

transfer 2.292 grams of anhydrous na2hp04 previously dried at 105 ℃ to a constant weight into a 500 ml flask. Dissolve in about 100 ml of water, dilute and mix

ammonium molybdate solution (acidic):

● part a: add 50 ml of nh4aoh (concentrated) to 300 ml of water

add 80g ammonium molybdate [(NH4) 6mo7o24 × 4h2o] (molecular weight =1235.9) and heat to dissolve. Cool and mix

● Part B: add 400 ml of concentrated HNO3 (concentration = 1.41 g/ml) to 300 ml of water

finally, drip part a into Part B for permanent mixing


accurately weigh 1 at an accuracy closest to 0.001 grams 0 g sediment sample and transfer the sample into a 250 ml conical flask. Add about 100 ml of 1:1 nitric acid and boil slightly to completely dissolve the sample and expel Brown NOx smoke. Then cool and transfer the solution into a 250 ml flask, label and mix (solution a)

transfer 20 ml of the solution sample into a 200 ml beaker, add 100 ml of water and 5 ml of 4% kmn024. Boil for a few minutes, then titrate and add 30% NaNO2 to eliminate excessive kmn024 and MnO2. Boil for a few minutes to remove nitrogen oxides

cool and neutralize to pH with 25% nh40h (measured with pH meter). Add drops of (1:1) HNO3 to dissolve the sediment. Plus, each person will use an average of 45 plastic bags to put 10 grams of NH4N03. Heat to 45 ° -50 ℃ (using water bath), drop 50 ml of acidic ammonium molybdate solution and 2 drops of 25% NH4OH. Mix the solution and sediment for minutes and let stand for hours

filter the solution through a gravity glass filter ("F" or "4" hole) with the largest hole of 5 µ M. Use a small amount of solution (2% hn03 + 5% NH4N03) to clean the sediment times, and cool the deionized water (without CO2) until the phenolphthalein test (5 drops of cleaning water + phenolphthalein + 1 drop of 0.1 N NaOH = pink) shows that the cleaning material does not contain acid. Dry the filter and sediment in an oven at 110 ℃ for hours. Cool and weigh in the dryer

calculation formula:


a - the weight of filter and sediment (NH4) 3p04.12mo03, in grams

b - the weight of the filter, in grams

c - the weight of the sample placed in 20 ml of solution, in grams

photometric method has the advantage of more economical instrument and can be used selectively. It is found that the phosphorus determined by molybdenum vanadium phosphoric acid method can achieve better accuracy and greater sensitivity [4]


phosphorus solution (0.4 mg/ml):

transfer 40 ml of 1 mg/ml standard solution into a 100 ml flask. Add 15 ml of (1:5) hn03, dilute and mix

ammonium molybdate solution (100 g/L):

add 100 g of ammonium molybdate [(NH4) 6mo7o24 × 4h2o] dissolve in 600 ml of 50 ℃ water and dilute to 1 liter. Filter before use

ammonium vanadate solution (he said: "we treat Blake like ordinary people treat concept car 1, 2.5 g/L):

dissolve 2.5 g of nh4v03 in 500 ml of hot water. When the dissolution is complete, add 20 ml (1:1) Hn03, cool and filter as needed, and dilute to 1 liter

summary of photometric methods

when excessive molybdate solution is added to the acidified mixture of vanadate and orthophosphate, a yellow complex will be formed. Photometric measurements were made at approximately 470 nm

phosphorus calibration curve of vanadate and molybdate (photometry) method


transfer 1.5 ml of solution sample (from solution a) into a 150 ml flask, add 20 ml (1:5) of hn03, and then cover it. Boil slightly for about minutes. Add 2 ml of 1% kmn024 solution and heat until just boiled. Add 1 ml of 3% H202 solution and shake the flask until too much kmn024 is dissolved and the solution is transparent. Add 10 ml of vanadate solution and boil slightly until the solution turns clear, luminous blue-green, indicating that too much H202 has been dissolved. Cool to room temperature. Transfer the solution into a 100 ml flask and dilute with water to about 80 ml. Add 10 ml molybdate solution, dilute and mix. The color of the phosphorus complex is formed within 5 minutes and stabilized for at least 1 hour

the recommended concentration range in 100 ml solution is 0 2 mg phosphorus. At 470 nm, measure the absorption rate of the sample and the calibration solution, which is one of the first environmentally friendly plastic packaging materials on the market. Plot the photometric readings of the calibration solution and the content of phosphorus per 100 ml of solution. Use the calibration curve to convert the photometric reading of the test solution to the phosphorus content

calculation formula:


a - the content of the sample used in the photometry

b - grams of sample (250 ml)

Table 1 and table 2 show that the successful method can easily and accurately determine the content of phosphorus in electroless nickel plating deposits without major systematic errors


1 Fredericka A. Lovenheim, "Modern Electroplating", Third edition, 1974, p.721.

2. Ponomarev A., "Methods of chemical analysis of minerals", Vol. 2., Moscow, 1955, p..

3. Teplouchov V., "Express analysis of steels", Third edition, 1971, p..

4. ASTM, " Annual book of ASTM Standards", 1985, Method E156, p. .

about the author

Dr. Vera persits received a master's degree in chemistry from the State University of Rostov, Russia, in 1971, and a doctor's degree in analytical chemistry from the State University of Leningrad (currently known as St. Petersburg) in 1982. His doctoral research topic is "investigation of electrothermal atomization process and its use in the determination of zinc, cadmium, lead, tin, bismuth and antimony in steel and alloys". Dr. Vera persits has written and co authored more than 20 papers and obtained two patents for analytical chemical screw. Since 1992, Dr. persists has been a chemical engineer in the field of IAI electroplating. (end)

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