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Pretreatment process is one of the most important and essential part of the Powder Coating or Painting process. As all the materials which has to be Powder Coated / Painted has to be totally cleaned and free from dust, oil, rust, scale and any other impurity on the surface.
The process which is adopted for the above is known as Pretreatment Process. The process comprises of the seven or eight tank system and the material is to go through different chemical process and the end result is the totally cleaned surface of the metal with protective coat.
The seven stages are as follows:-
For removing of oil, dust and any greasy substances. The chemical is basically alkaline and made as 15% Strength in water. The chemical is heated up-to 60 degree. The jobs are then dipped in solution for 5 min and due to Chemical reaction all the dust, oil and greasy substance is removed.
• Water Rinse
For cleaning and removing the excess detergent. The plain water is in the tank and when the components are dipped, excess detergent is removed and the Components are washed.
For removing the rust and scale on components. The chemical is basically acidic and a solution of 15% in water is made. The components are dipped for 5-7 min depending on the amount of rust. The components then become virgin and ready for next process.
• Water Rinse
The excess chemical is washed in the water.
For giving a adhesive coat on metal. The solution is made of 10% in water. The components are kept in the solution for 5-10 min depending on the Coating required on the jobs. The solution is generally heated up-to 60-70 degree.
• Water Rinse
For removing excess solution.
For giving a protective coat on the phosphated job. The solution is made of 5% strength. The chemical is heated up-to 60 degree C. The jobs are then dipped in solution for approx 2-3 min and a protective coat comes on the job.
After the above process the metal is ready for Painting or Powder Coating.
For Aluminium & Brass Components.
The pretreatment process of the Aluminium and Brass components are different from the MS.
In above components cleaning procee is is of three stages as follows:-
1. Degreasing : To clen the extra oil and grease on the components.
2. Water Rinse : To wash out and remove the excess degrees material from theComponents.
3. Passivation : To make the surface active for the acceptance of Powder.
However a short cut for the cleaning of MS components are as follows:
3.Dip in Three in One solution for phosphating and passivation.
Then the components are taken , dried and Powder Coated. / Painted
For casted or forged components generally they are shot/sand blasted and then powder coated/ painted. However these components are to be coated within one hour of being shot/sand blasting as they are prone to catch the moisture from atmosphere and turn yellow.