Paint Thickness Gauge (PTG)

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Paint Thickness Gauge (PTG):

Most paint thickness gauges work by sensing the distance between the sensor and the metal base material. That’s total distance, which would be the thickness of all layers (primer, base, colour, and clear coats) and any repainted material, etc. You have to take an educated guess as to how much each layer consists of.

Contents

Why Use a PTG?

Using a paint thickness gauge gives a professional detailer credibility and also acts as an insurance against ‘break-though’ of a clear coat, which would entail a re-paint and I suspect a very irate customer. Original paint has a better resale value than a re-painted vehicle, plus they will lose the use of their vehicle for some days. The ideal setup would be a DFT Combo for the metals and a PosiTector 200 B/Adv for the composites.

Usage

A paint thickness gauge for use in the detailing industry requires fine measuring resolution in increments of 0.1 mil (0.0001= inch) is typical. Therefore you should choose a paint gauge with a minimum 3% accuracy and a 0.1 mil (2 micron) measuring resolution. 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 available, check is periodically during the process and on completion to see how much was removed. Take measurements with a paint and coating thickness gauge and mark them on a template so that you have a reading of before / after polishing.

Take readings on each panel left – right every 2- 4 inches, then drop down 2-inches and repeat. – Paint Thickness Template - [1]

If you use a car outline template and mark the paint thickness, you can advise the customer of any potential problems and you’ll also have a permanent record of the customers paint surface, which can be used as a reference each time the car is polished.

Select substrate:

  • F - for ferrous metals (steel and cast iron)
  • N - for non-ferrous metals (aluminium, copper, brass, etc.)
  • FN - for all metal substrates, gage automatically recognizes the substrate and takes measurement

PTG Technologies

Magnetic Induction

Using this technology the thickness gauge utilizes non-destructive principles when measuring coatings on Ferro-magnetic substrates such as Steel and Iron. The coatings must be non-magnetic such as; paint, enamel, aluminum, chrome, copper and brass.

Eddy-Current

This technology utilize a non-destructive principle when measuring coatings on non-magnetic substrates such as; aluminum, aluminum alloys, bronze, copper, brass tin and rustproof weak magnetic steels. The coatings must be electrically insulating such as; paint, enamel, plastics, anodized coatings and ceramics.

Ultrasonic

An ultrasonic transducer emits a high frequency sound pulse that travels into the coating via a coupling gel and reflects from ANY surface that is different in density. Coating thickness readings are obtained by measuring the time taken for the ultrasonic signal to propagate from the probe to the coating/substrate interface and back. The travel time is divided by two and multiplied by the velocity of sound in the coating to obtain the thickness of the coating. In some circumstances, individual layers in a multi-layer system can be measured.

General Information

Most OEM paint finishes range from 4 to 8 mils , 1 Mil=1000th of an inch (100 - 200µ 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 delaminating 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.

Most OEM paint finishes range from 4 to 8 mils (100 to 200 µ (microns)) 100 – 200µ 4 – 8 mil - normal paint thickness 80 – 100 µ - 3 – 4 mil, thin paint >80 µ - less than 3 mil, very thin paint

German and Japanese cars: 4-5 Mils 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 information only

It’s interesting to note that painters must now demonstrate proficiency with an electronic paint thickness gauge in order to become certified to perform paint refinish warranty work for General Motors Corp. (GM) vehicles.


How-To-

Paint Thickness Gauge (PTG) - most paint thickness gauges work by sensing the distance between the sensor and the metal base material. That’s total distance, which would be the thickness of all layers (primer, base, colour, and clear coats) and any repainted material, etc. You have to take an educated guess as to how much each layer consists of.


A paint thickness gauge for use in the detailing industry requires fine measuring resolution in increments of 0.1 mil (0.0001” ) is typical. Therefore you should choose a paint gauge with a minimum 3% accuracy and a 0.1 mil (2 micron) measuring resolution. 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 available, check is periodically during the process and on completion to see how much was removed.


  • Take measurements with a paint and coating thickness gauge and mark them on a template so that you have a reading of before / after polishing. Take readings on each panel left – right every 2- 4 inches, then drop down 2-inches and repeat. – Paint Thickness Template - Image of Detailing Template - Photobucket - Video and Image Hosting


Using a paint thickness gauge gives a professional detailer credibility and also acts as an insurance against ‘break-though’ of a clear coat, which would entail a re-paint and I suspect a very irate customer. Original paint has a better resale value than a re-painted vehicle, plus they will lose the use of their vehicle for some days. The ideal setup would be a DFT Combo for the metals and a PosiTector 200 B/Adv for the composites.


  • If you use a car outline template and mark the paint thickness, you can advise the customer of any potential problems and you’ll also have a permanent record of the customers paint surface, which can be used as a reference each time the car is polished.

If you have any questions I'd be glad to attemp answers-


DeFelsko PosiTest DFT - series of gauges measure coatings up to 40 mils (1000 microns) making them ideal for non-destructive measurement of automotive paint thickness on a variety of metals. a) DFT Ferrous is ideal for measurements on steel panels

b) DFT Combo is available for measurement requirements on both steel and aluminium panels. With 3% accuracy and a 0.1 mil (2 micron) resolution Either PosiTest DFT model provides the capability to measure the amount of paint removed while sanding and buffing. DeFelsko - http://www.defelsko.com/PosiTestDFT.htm Or Detailers Domain - http://www.detailersdomain.com

c) PT200 Ultrasonic Thickness Gage - this revolutionary meter measures paint thickness over non-metals such as fibreglass panels, plastic bumpers and interior components, approved for use in BMW’s dealer equipment program – DeFelsko - http://www.defelsko.com/p200/positector200.htm

d) PosiTector 200 will work on composites (plastics, carbon fibre, fibre glass, etc). The ideal setup if memory functions for metals aren't important would be a DFT Combo for the metals and a PosiTector 200 B/Adv for the composites (these two PTM approx $1000).

e) PosiTector® 6000 Series (composites; plastics, carbon fibre, fibre glass, etc you will want the FN or FNS models as they work on all metals) rugged, fully electronic coating thickness gages use magnetic and eddy current principles to measure coating thickness on both ferrous and non-ferrous metals, accurately and quickly. SSPC PA2 feature set determines if film thickness over a large area conforms to user-specified min/max levels - http://www.defelsko.com/pt6kFR.html

DeFlesko Applications -Italic text http://www.defelsko.com/applications/automotive/automotive-paint-detailing.htm

f) Alibaba Coating Thickness Meter CM8828 Operating principle: Magnetic induction / eddy current (F / NF) measuring range: 0-1250um / 0-50mil Resolution; 0. 1 / 1, Accuracy: + / - 1-3% n or + / -2. 5um, it meets the standards of ISO2178 and ISO-2360 as well as DIN, ASTM and BS. Suitable for the laboratory and for use in harsh field conditions The F probes measure the thickness of non-magnetic materials (i.e. paint, plastic, porcelain enamel, copper, zinc, aluminium, chrome etc.) on magnetic materials (i.e. iron, nickel etc.) .

Often used to measure the thickness of galvanizing layer, lacquer layer, porcelain enamel layer, phosphates layer, copper tile, aluminium tile, some alloy tile, paper etc. The N probes measure the thickness of non-magnetic coatings on non-magnetic metals.

It is used on anodizing, varnish, paint, enamel, plastic coatings, powder, etc. Applied to aluminium, brass, non-magnetic stainless steel, etc Automatic substrate recognition - Colead Industrial Co., Ltd. China Alibaba - http://www.alibaba.com/catalog/12154433/Coating_Thickness_Meter.html

g) QuaNix Handy measures steel and alloys in 0.5 Mil increments - http://www.automation-usa.com/products/


Information resource- Automotive Detailing Inside & Out, A Knowledge Base for the Perfectionist"– by Jon Miller

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