To achieve best practice in body preparation, refinishers must follow the key steps and avoid the common pitfalls. DuPont Refinish gives some advice to ensure the perfect finish.

Know your substrate and keep it clean
As basic as it sounds, it is absolutely vital for refinishers to know which substrate they are dealing with, such as composite or galvanised steel. For instance, to sand bare aluminium, refinishers should use a fine grade of abrasive, to avoid creating deep scratches or generating too much heat, which can distort thinner sections of the panel. It is also important to remember that if the substrate is galvanic, corrosion can occur by cross-contaminating aluminium with steel. This is only completely avoidable within a dust and dirt free environment, and by using designated tools.
 
Use the right grade of sand paper
If refinishers do not use the right grade of abrasive paper, it can lead to scratches showing through into the topcoat.
The sanding operation should always be carried out in conjunction with a good quality dry guide coat, which should
be applied to the repair area before
moving to finer grit abrasive. This enables
the refinisher to see any minor defects
in the repair area.

Clean and degrease properly
An important aspect of body preparation is full and careful degreasing and appropriate cleaning of the panel before starting the refinishing stage. Refinishers can use DuPont Refinish 3608S Prepclean, which eliminates non-water-soluble contaminant, such as wax, polish, tar, silicon and grease, from old finishes. This should then be followed by DuPont Refinish 3910WB Waterborne Prepclean, which removes all water-soluble contaminants. Cleaning the vehicle at this stage, allows the refinishers to make an accurate assessment of the damage, and also makes refinishing easier and less prone to contamination. Refinishers need to demonstrate perfect hygiene at this point otherwise this can affect the final finish. By regularly changing gloves, and having separate overalls for preparation and a pair for painting, refinishers can achieve a better end-result. Once the vehicle is at the priming stage refinishers should again use a preparatory cleaner, like DuPont Refinish 3910WB Prepclean, to eliminate any contaminant that may have settled on the repair area. They should also use a clean tack cloth over the prepared area, so that a perfectly clean surface is obtained before the application of subsequent undercoats. Use DuPont Refinish 3911WB Final Clean for the next degreasing steps in the repair process.
 
Use an etch primer
Many refinishers do not use an etch primer in the refinishing process. This is a critical error, as the etch primer plays a very important role, giving the best possible adhesion between the substrate and the subsequent layer. For example a 2K primer renders the paint layer impermeable to moisture preventing micro blistering at a later date. Refinishers can opt to use DuPont Refinish 635R, an etching primer, or wash primer surfacer 825R used as etching primer. Both provide excellent long-term protection against corrosion and blistering of bare metal.
 
For more information please refer to the Technical Data Sheets available on www.dupontrefinish.eu or contact Crown Paints on 01-816-4447, or you can read this article as it appeared in the May 2013 issue of Autobiz.