"ZINPHOPHOS – HZP" is designed to provide heavy ZINC PHOSPHATE coating with thickness of 300mg/sq.ft within 15 – 20 minutes on iron & mild steel components by simple immersion method. A dense, heavy adherent coating obtained by this method and prevents excessive wear and tear of moving parts of machinery. This coating serves as base for paints as well as for Rust preventive oil coating. It is operated at a temperature of 80 – 90o C
Bath Make up : The tank should be free from grease, oil, rust, scale, etc, and should be coated with FRP or PVC or non – reactive material to bath solution.
For optimum results and maximum life of solution regular testing should be done using the analytical procedures outlined under the heading “control ”.
During the phosphate process, ferrous ions build up in the solution. If the ferrous ion contents exceeds 0.4%, it affects the corrosion resistance and performance of coating. So, Ferrous ion should be checked and maintained below 0.4% by either discarding the solution completely or partially. The method of analyzing the ferrous ion content is given under the heading "control".
During the operation of phosphate process, sludge a natural by – product of the Chemical reaction is formed slowly at the bottom of the tank. The bath solution should not be stirred up while jobs are being processed, otherwise dusty coatings may result. The sludge should be removed from the bath preferably twice or thrice a month
To obtain good coating, it is necessary to maintain the bath at the specified operating temperature. If the temperature increases more than the specified temperature, white loose powdery coating is obtained. If temperature decreases, results in bluish rust appearance.
The total Acid (Pointage) of the bath solution should be maintained between 28 to 32 points.
To find the total acid pointage (Total acidity). Stir the bath and take 10CC of bath solution into conical flask. Add 5 to 6 drops of PHENOLPHTHALEIN indicator. Titrate against 0.IN NoaH solution,
It will give 28 to 32 points reading which represents the total pointage (Total Acidity) of the bath solution. To raise the pointage, add 1.45 litres of “ZINPHOPHOS – HZP” per 1000litres of bath for one pointage increase. It is recommended to maintain the pointage by regular additions of the chemical periodically.
To find free acidity take 10Ml bath solution and add 3 to 5 drops of BROMOCRESOL GREEN indicator and titrate against 0.1N NaoH solution. The result is yellow to light green colour change. The pointage should be 2 to 3
Dip a strip of Starch Iodide paper in the bath. With in half a minute the colour will change revealing the accelerator strength in the bath, as given below
Pipette out 10ml of bath solution into a conical flask, add (3~5ml) of sulphuric acid (50% Concentration) to it. Titrate against 0.1N potassium permanganate solution, the result is colourless solution changes to permanent pink colour.
No of ml 0.1N of KMno4 required * 0.056 = % of Ferrous ion.
The components to be phosphated should be free from oil, grease, dirt, rust, scale etc,.
Generally, the following process cycle is adopted for M.S. components
Trichloroethylene vapour degreasing is the best method. This process is recommended where heavy oil and grease are present on the job and good quality of cleanliness is desired. This process is highly expensive. Alkaline and Emulsion degreasers are also used for degreasing. It is easy, very economic and operator friendly process.
Rinse the job in a clean cold continuously overflowing water for few minutes.
An acid pickle should be employed where rust, scale and oxides are present. For iron castings, high carbon steel, and for quality phosphating, phosphoric acid base composition is recommended for pickling process. Phosphoric acid base pickling processes are costlier when compared to Hydrochloric or Sulphuric acid. Normally, Hydrochloric acid or Sulphuric acid is used for pickling with proper inhibitor. Proper inhibitor should be used; otherwise the inhibitor film will interfere with phosphating process
As described in the heading “PROCESS”.
After phosphating, dip the jobs for 1 minutes in 1% hot “PASSIVAT – HZP” solution to seal the phosphate film and to remove surface acidity for improving the corrosion resistance and paint adhesion.
1. Degreasing : 5 - 10 minutes.
2. Rinsing : 15 - 30 minutes.
3. Pickling : 5 - 10 minutes.
4. Rinsing : 15 - 30 minutes.
5. Phosphating : 10 - 20 minutes.
6. Rinsing : 15 - 30 minutes.
7. Passivation : 1 - 2 minutes.
Selection of equipments, such as type of tanks, size of tanks, type of heating and handling devices etc., depends on the production rate and type of jobs to process.
“ZINPHOPHOS - HZP” is acidic and oxidizing in nature. Normal safety precautions such as rubber gloves and aprons as well as safety glasses should be worn when handling these chemicals. In case of contact with skin, wash with plenty of cold water and for eyes, flush with plenty of pure cold water and seek medical attention immediately.
Priyadarishini Chemicals is engaged in Manufacturing of Automobile and Industrial Speciality products from INDIA since 1997 with the aim of providing premium quality products to its valuable customers.
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