The steam phosphating process is not only done in a single operation, but significantly reduces the initial investment and all costs related to water and its management. Saturated or dry steam is widely used in the treatment of surfaces before painting, or for protective treatments. Saturated steam, as well as being very effective for cleaning and degreasing parts, is also an excellent conductor for phosphating / passivating products. This means that, with a single operation, the operator completely prepares the piece for the painting phase.
For each REA steam generator, there is a phosphating version, with an additional tank for the product and specific components in stainless steel.
Phosphating is a chemical process by which the surface of a metal material is altered, creating phosphate crystals chemically bonded to the substrate in order to exploit the properties of these compounds to improve resistance to corrosion and favor the adhesion of the subsequent painting.
Phosphating is a commonly used procedure for iron and ferrous alloys; is the most common preparation treatment for painting steel sheet. The phosphating treatment uses phosphate solutions (zinc phosphates, iron, manganese, nickel phosphates), to cover the surface with a protective crystalline layer (5 – 10 µm thickness) of phosphate which gives high resistance to corrosion and improves the adhesion of the next layer of paint thanks to the increase of the surface micro-roughness.
The process is carried out in spray or immersion systems, normally integrated with the degreasing ones. Both the spray and immersion solutions are complex and require multiple operations:
- Possible manual deoxidation at room temperature
- First spray pre-greasing 30 s at 60 ° C
- Second spray pre-greasing 60 s at 60 ° C
- Spray / immersion / spray degreasing 30/240/30 s at 60 ° C – pH 11-12
- Spray / dip / spray wash 30/60 / 30 s at temp. environment
- Spray / dip / spray activation 30/60/30 s at temp. environment – pH 9-10
- Immersion / spray phosphating 180/30 s at 52 ° C – pH 2-3
- Spray / dip / spray wash 30/60/30 s at temp. environment
- Passivation spray / immersion / spray 30/60/30 s at temp. environment – pH 8-9
- H2O washing demi spray / immersion / spray 30/60/30 sec at temp. environment
- H2O rinse half 2 – 3 ramps at temp. environment
- Drying 15 minutes at 140 ° C – 160 ° C (optional), depending on the subsequent painting process (eg.
- Cataphoresis and / or powder coating)
Furthermore, both of these techniques involve large and costly baths / tunnels, not to mention the consumption of water and, consequently, the corresponding quantity to be disposed of. The REA STEAM CLEANING steam phosphating process is not only done in a single operation, but significantly reduces the initial investment and all costs related to water and its management.
Passivation is an electrochemical phenomenon that can slow down or completely prevent the corrosion reaction of metallic materials that otherwise the latter would undergo. The phenomenon basically consists in the formation of a thin film (consisting of corrosion products, substances present in the aggressive environment or oxygen adsorbed on the metal surface) which adheres perfectly to the part of the surface of the piece in contact with the aggressive environment (for example water or air). For the passivation phenomenon to occur, the film must hinder the diffusion of the oxidizing agent (generally oxygen), so it must be “compact”, ie dense and not very porous.
As in the case of phosphating, dry or saturated vapor can be used to conduct the passivating product to the surface.