Hi Everyone,
Thanks once again for looking at my blog.
Today's blog post was a special request from the guys at the VW Watercooled forum.
So to start off let's cover what failing cleat coat is and what causes it.
Layers of Paint
When a modern car is painted there are three distinct layers of paint:
1. The primer or basecoat. This is the first layer or paint that is sprayed down over the bare metal, plastic or composite body of the car. The colour of this will depend on what colour the final car is going to be but it is almost always either grey, white or black.
2. The colour coat. This, as the name suggests, is the layer of coloured paint which you can see once the car is painted. This varys depending on what colour you, or the previous owner chose for the vehicle. It can either be a solid colour or a metallic colour. If Metallic or Mica then the paint has been mixed with different coloured flakes of metal or natural Mica. There are many different coloured flakes available for example red cars can have gold metallic, such as Mazda's Copper Red Mica, black cars can have blue flake, such as Ford's Silhouette and silver cars can have silver flake like VW's Reflex Silver. The type of flake varys between manufacturer.
3. The clearcoat. The clearcoat is the very top layer of paint on the vehicle. As the name suggests this coat of paint is clear. Clearcoat varys widely between manufacturers. Some, like Honda's, are sticky which makes them harder to polish, and some like Subaru, are soft, which means they mark easily and some like VW, Audi and Mercedes are very hard due to using a specialist clear called cerramiclear. This means they require special cutting compounds but are very durable and yield a great finish.
It is the clearcoat that you polish, wax or seal and it is the clearcoat that has to deal with all the environmental damage such as bird droppings, jet fuel, industrial fallout and mineral etching.
Why Does Clearcoat Fail?
So now we have an understanding of what clearcoat is we can look at what causes it to fail.
There are three main causes to clearcoat failure:
1. First is impropper paint bonding. This occurs when the clearcoat is layed down incorrectly over the colour coat. The bond between the two is not achieved and as such the clear will slowly begin to bubble and peel from the vehicle. This picture shows the failing clear on the left hand side of the boot lid. The right hand side had a filler wax applied to mask the problem for the owner.
2. The second is removal of too much clearcoat. This often occurs when the vehicle has been agressively buffed a number of times or if the vehicle has been wetsanded by an inexperienced operator. This leaves the clearcoat thin and as such it's UV blockers are removed and it gives in to the effect of the harsh Australian sun.
Image care of Autogeekonline.net
3. The third is lack of protection. Some people just don't look after their cars and as such the paint work never saw any wax or sealant. Over time the effects of the environment took their toll and you're left with a mess that needs to be sprayed to be fixed up.
Slowing Failing Clearcoat
So your clearcoat is failing, what can you do to stop it? Well in short, nothing. Once the process has started it can't be stopped. You can however attempt to slow it.
If your clear is peeling due to a poor bond with the colour coat or insufficient film build there are a few things you should do:
1 . Always wash and wax or seal from the strong side of the clear to the failing side this will prevent you from getting contaminates and solvents stuck under the failing clear. It will also mean that you do not lift the edge with your cloth or app pad.
2. Use a good quality wax or prefrebly a sealant with both UV-A and UV-B blockers. Examples of these are Duragloss 105 , Zaino Z2 Pro and Nanolex paint sealant. This will restore the UV blocking properties and assist with the slowig down of the clear failing.
There are also a couple of things not to do:
1. Pressure washing. If the jet of the pressure washer hits the failing clear then it cause it to lift, further exasperating problem.
2. Abrasive polish. If the clear is already failing there is no need to help it along by thinning it out further. Even light polishing may make the situation worse so it is best to stay away all together. If you are massively concerned with swirl marks then use a filler polish such as Autoglyms Super Resin Polish or Ultra Deep Shine and top it in Autoglym Extra Gloss Protection.
Preventing Clearcoat from Failing
So what if your clear is fine? How can you stop it failing?
1. The main thing to do is always use a quality carnauba wax or a quality synthetic sealant. This will act as a barrier between the environment and your paint. This sacrificial layer will take the force off the bird droppings, jet fuel and mineral etching meaning your clear coat stays in pristine condition.
2. Secondly be wary of who machine polishes your vehicle. A lot of unskilled tradesmen will use agressive cutters that will remove a lot of marks but also a lot of paint. Ensure that anyone that is agressively correcting your vehicle either through machine polishing or wetsanding is experienced as is using a paint thickness gauge (below) to assess how much film build remains between all the steps.
As always feel free to ask any questions or leave comments.
Dan
Monday, February 22, 2010 at 10:58PM 
