Paint Film Thicknees

From DetailingWiki

Paint Film Thickness:

Automotive paint systems comprise of up to five different layers of paint. The system typically consists of:

• A galvanized steel substrate with a thin crystalline tri-cation phosphate treatment to enhance adhesion and improve corrosion protection;

• An E-coat is then added which is the first protective layer. This is electrodeposited and then cured

• Lower panels have an anti chip layer, which is a thick layer designed to give protection against impact from stones

• This is then followed by a primer (2.0 Mils) and a basecoat (1 – 2.0 Mils) layer, which is the colour layer

• And finally polyurethane clear coats 2 – 3.0 Mils. The clear coat provides protection from a hostile environment and an excellent brilliance, but is easily scratched; once it is compromised repairs involve re-painting, as the base colour has no brilliance, shine or depth, start with the least abrasive product to accomplish desired results, and only if necessary move up to the next grade of abrasive.

Q: What is the "right" paint thickness for a vehicle?

• There is no "right" paint thickness for any vehicle. Automobile manufacturers paint thousands of vehicles each day with a wide variety of paint formulations; their specification has a range of thicknesses. For some models this can be as low as 3 Mil and, in the case of the rocker panels of Sports Utility Vehicles (SUVs), as high as 17 Mils.

Q: If there is no "right thickness", what am I looking for?

• Paint thickness consistency; for example, when you are reading between 3.5 and 5.0 Mils and a reading shows a sudden reduction in thickness, you know there is a cause for concern in that particular area of the bodywork.

Most factory paint jobs range from 3.5 to 5.5 mils (87 to 137 microns) (this will vary between manufacturers) for this reason, it’s also recommended that paint be measured when buffing since you can’t see how much paint is being removed during the buffing process. If an insufficient thickness of clear remains after polishing premature failures such as fading or delamination may occur as the colour coat won't be protected from ultra violet (UV) radiation and a warranty issue may develop in the future. Such risks can be alleviated by monitoring and minimizing the amount of top coat removed, which is best done through quick and easy measurements with an electronic paint gauge, and maintaining a record on a paint thickness template.

• German and Japanese cars: 4-5 Mils (1 Mil=1000th of an inch)

With the exception of:

• Lexus-White and Tan: 5-7 Mils, Lexus- Black and Silver: 4.5-6 Mils

• BMW: Silver: 6-7 Mils

• FORD: Approx. 5.5-7 Mils

• GM Cars and Trucks: Approx. 4.5-6.0 Mils, Jimmy’s and Blazers: approx 7 Mils

• Chrysler: Approx. 5.5-7 Mils (Note Sebring hoods are fibreglass)

• Dodge Cars: Similar to Chrysler

• Dodge Trucks and newer Ram Pick-ups: Cab approx. Mils and the boxes approx 9 Mils

• Jaguar: approx. 6-7.5 Mils (but they tend to vary)

• Jeep Grand Cherokee: These read approx. 6-8 Mils, Wranglers: approx. 4.5-5.5 Mils

Note- the above are provided for guidance / information only

Paint Thickness Gauge (PTG): An electronic paint thickness gauge can be an invaluable tool, before buffing it’s always a good idea to check the paint film thickness to see how much of the paint film thickness is available, check periodically during the process and on completion to see how much was removed. Take measurements with a paint and coating thickness gauge (Check-Line Model DEF-900)

All the major car manufacturers specify that measurements should be taken before, during and after these steps. This is primarily because removal of too much clear coat can cause paint failure over time due to the fact that UVR absorption is the job of the clear coat. If an insufficient thickness of clear remains after polishing the colour coat won't be protected from UV radiation.

For this reason, it’s also recommended that paint be measured when buffing since you can’t see how much paint is being removed during the buffing process. If too much clear is removed, either on the original OEM finish or the refinished areas (colour coat 0.3–0.5 and total paint 1.8MIL thickness min) a warranty issue may develop down the road it’s interesting to note that painters must now demonstrate proficiency with an electronic paint thickness gauge in order to become certified to perform refinish warranty work for General Motors Corp. (GM) vehicles.

Information resource -

• “Automotive Detailing Inside & Out, A Knowledge Base for the Perfectionist"– by Jon Miller aka TOGWT™ "