Underbody Coating
UNDERBODY COATING-
Coating word indicate itself ,to creating preventing layer on the metal surface to prevent from rust ,corrosion.Coating contains various form like powder coating,liquid bath coating,spray coating etc..
In underbody coating ,there will be provision of corrosion resistive film on automotive body parts.The undercoating done in automobile because it grab the all complex portion of body parts which is not possible by Sprey or powder coating.
In underbody coating containing coating ingradient in the form of liquid.The liquid form used due to it's special property like flowability and viscocity character.The liquid form can easily pass through any complex shape and maintain same thickness of coating with genarating proper coating film on car body as per specifications.
Process of underbody coating-
1.PRETREATMENT-
In pretreatment,the BIW body in sequentialy dipped into liquid bath.In this stage first body will cleaned by removing oil,weld spot bur to obtain the clean and plane BIW body.
The clean and dust removing body is ready to next stage of degreasing,conditioning and phosphating process.The Phosphate coating layer provide anticorrosive property which help to stop the spreading of corrosion phenomenon.The pretreatments create the joint bitween body and coating layer that could attach the other coating layer.
2.ELECTRODPOSITION-
In this stage the BIW body passes through deep liquid bath.In this electric current as well as liquid electrodiposition paint is passed through the body.The mixture of resin ,binders,and solid paste pigments are stored in liquid tank.The body will moving into the solution containing mixture of water and electrodeposition paint ,resin ,binder and paste pifments.The pigments are used to gain the color and gloss and resin used to provide anticorrosive property.
After electrodeposition coating bosy moved to Bake oven in that body is heated at set temperature at 10 to 15 min duration.
3.RUST PROOF MATERIAL-
In this coating stage the body is coated as well sealed at joint section with the help of PVC or urethens.The high elastic resin also used bitween primary coating and electrodeposition coating at front hood section which help to reduce shock.
4.PRIMER COATING-
In this process ,the gap and scratches that may occures during previous coating process are improved by primer coating.The grinding and sanding process used to remove imperfections.The primer provides corrosive resistive property and increases the paint durability.
5.TOP -COAT
TOp-coat is final step to underbody coating of BIW body also in involve further two process like Base coat and Clear coat.
A) Base-coat- It is applied after primer and before clear coat and it is primary coloring coating process.In base coating thousand of color coat are available.
B) Clear-coat-It is final coating process of car body.It provides coating durability ,scratch resistance to allover coating layers.It protect the coating from UV rays of sun and also provides gloss to surface of body.
PROS AND CONS OF UNDERCOATING-
A) PROS-
- undercoating gives better coating quality.
- uniform and consistance of coating will be applied.
- It gives corrosion resistive property.
B) CONS-
- It is very costly process.
- corrosive property maintained difficult at different conditions.
- the binding agents and resign quantity should be maintained.
- it gives best result on new car.
# CONCLUSION-
Understanding the process of automotive BIW coating process,it's importance and various steps are followed through underbody coating process.The underbody coating gives best result than previous coating process.