Pre-treatment or surface preparation is done by removal of all foreign particles & rust, giving a layer of phosphate for good adhesion of paint. Pre-treatment is done by following process of dipping in tanks by help of electric hoist of 3 ton capacity running over the tanks, the process flow below.
The machinery include
- T-1 Degreasing Tank: Having alkaline media. The tank is heated to a temp of 60° C to 70° C.
- T-2 Water Tank: For Rinsing
- T-3 De Rusting: The acid bath removes all rust and exposes the virgin metal. The use of phosphoric acid as base, though expensive gives better ultimate quality of coating. Temperature of tank is about 50° C.
- T-4 Water Tank: For Rinsing.
- T-5 Surface Activation: Traces of acid are removed and made ready for phosphatising.
- T-6 Phosphatising Tank: The tank provides a fine layer of phosphate which helps in excellent adhesion of paint as well as it prevents the virgin metal to rust in oxygen & moisture laden atmosphere. Temperature of this tank is maintained at 50° - 55° C.
- T-7 Water Rinsing
- T-8 Passivation Tank: This tank is kept at 70? C and imparts stability to phosphate layer.