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Over the last 20 years, we have seen variations of basic colors that have stretched the imagination. The color blue show hints of green, red or purple and many other colors. How is this possible? In the old days, there were the basic colors of red, blue, green, yellow, black and white. That was about it and you could pick your color of choice. Because the paint was a lacquer-based paint, this allowed for a lot of flexibility when repairing but did not have the durability of today’s vehicle paints. It was possible to repair a small spot in the middle of a door and paint the repaired area without removing all the components of the door or everything from the adjacent panel as is done now.
This is all possible due to the introduction of a 2 part refinishing system known as 2-stage or base coat clear coat. It all begins with what the manufacturer requests from the chemists who make the formula for the color. A manufacturer may want to have the best gloss and the surface to be resistant to scratches. They also will want the paint surface to be resistant to atmospheric pollution, such as acid rain, tree sap, bird droppings, stone chipping, etc. The manufacturer will almost certainly have to give up something to achieve something else. For example, if they want gloss they will have to give up a little durability. If their concern is durability, the gloss may not be quite as nice. Most car manufacturers in trying to keep costs down will opt to play a game of give and take with the clear coat surface. Some vehicle manufacturers apply a special primer to the front of the hood in order to reduce rock chips. This primer is chemically treated to be softer and gives the rock a softer base to contact upon impact.
At the factory, the vehicle body shell is submerged in a tank that contains anti corrosion chemicals with a zinc rich base. This process gets into the small areas that would be impossible to get to with a conventional sprayer. Then the shell is t submerged in tanks containing 2 part epoxy primers and sealers, which provide a good base for the paint to adhere to. The paint is negatively charged and sprayed via computer-controlled sprayers. This is the base coat part of the application process.
The next step requires the application of the positively charged clear coat. The clear coat is composed of resins and is urethane based. The clear coat positive ions draw the negative base coat outwards towards the clear coat. Within the base coats are pigmented flakes, which contribute to the final color. This is the reason why it is possible to view three similar vehicles that have the exact same paint code and see three different variances. The collision repair facilities have to match the variant color for a perfect match.
This article is intended to give a general overview of the differences in paint properties that have occurred in the past. There are new processes that will be discussed later.
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Source: http://ezinearticles.com/?Automotive-Refinishing&id=2119657
