Long Lasting Protective Finish
Steel when it is delivered from the rolling mill has a ‘mill scale’ coating which is created in the production process of the steel. Mill scale is a form of rust that must be removed if the paint finish is to provide adequate protection.
Witter Towbars is (at the time of writing) unique in the UK having invested in an inline Shotblast machine that is integrated into the paint line facility. Towbars are loaded onto a continuous track that passes through an inline ‘Shotblaster’ where almost two tonnes of shot are propelled at the bare metal from eight high speed blasting wheels at a velocity of 70 metres per second.
The machine, which is almost as large as a small house, cleans thoroughly any trace of mill scale and rust from the surface. The ‘clean’ towbars are now very vulnerable and need to have a protective coating applied very quickly to prevent any rust developing. (Steel that has been thoroughly cleaned of all surface rust and contaminants can start to rust within a few minutes in the UK atmosphere). This is the big advantage of having a Shotblast machine integrated into the paint line facility.
The towbars after leaving the Shotblast machine are immediately passed through a seven stage zinc phosphate pre-treatment system in which the bare metal surface is chemically prepared to ensure effective adhesion of the final powder coating. Zinc phosphate is used rather than the more common iron phosphate pre-treatment. Zinc provides a higher quality of protection than iron, and is a more complex and expensive process.
The towbar continues its journey into an oven to remove any trace of moisture on the surface before having the powder coating applied. Four automatic oscillating guns apply a very durable automotive specification resin coating (paint finish) which is then cured at temperatures of approximately 220 degrees Celsius. The powder coating provides a robust and long lasting protective finish to the towbar. You can have confidence that the paint finish is built upon layers of technology designed to meet the arduous conditions experienced in its lifetime of towing.
All paint finishes are not the same, it’s what you cannot see that is vital for ensuring durability.
