Coating thickness gauges for non-destructive measurement – the QNix® series
What you should know as a user about coating thickness measurement and QNix® gauges
An electronic coating thickness gauge (also called dry film thickness gauges, paint meter or paint thickness meter) measures the dry film thickness (DFT) on metal substrates non-destructively. The coating thickness of dried wet coating, powder coatings, anodising and electroplating on metal substrates such as steel, iron, aluminium, zinc or copper can be determined, for example.
With its QNix® brand, Automation Dr. Nix offers a wide range of dry film thickness for precise and non-destructive measurement of coatings in a wide variety of sectors. We can look back and draw from decades of experience in heavy-duty corrosion protection, industrial painting and contract coating, surface finishing with galvanised and anodic coatings as well as vehicle assessment and bodywork.
- We work closely with our customers. Consequently, can we take specific requirements of different sectors into account in the further development of our coating thickness gauges.
- Our gauges are characterised by an easy and intuitive operation that is true to our motto of "place, measure, read".
- QNix® gauges are only developed and produced in Germany.
How thin is a micrometre?
How thick are these and those layers?
Measurement method for coating thickness measurement on metal substrates
Which role does the coating base play in coating thickness measurement?
How do QNix® devices focus on accuracy and what do accuracy, correctness and precision mean?
What must you pay attention to when using coating thickness gauges?
The QNix® series QNix® 1500, QNix® 4500 and QNix® 8500
A micrometre, a thousandth of a millimetre!
For most users the "micrometre" unit of measurement is merely a term. But can you really get an impression of how small a micrometre is, that is, 0.001 millimetres? A µm is a millionth of a metre and is unperceivable to the human eye. A human hair, for example, measures about 60 µm, and the oil layer that forms on water is only 10 µm thick.
The following examples are sorted in ascending order based on size:
- Nickel plating: from 3 µm
- Anodising: between 8 µm – 20 µm
- A human hair: approx. 60 µm
- Vehicle coating: from approx. 80 µm – 160 µm
- Heavy-duty corrosion protection: from 120 µm
- XPEL paint protection film (for protection from stone chips): 260 µm
- Fireproof coatings: up to several millimetres
Metallic substrates and their differences
A non-destructive QNix® coating thickness gauge measures the coating thickness on metal substrates. The coating base must either be magnetisable or electrically conductive for this purpose. Our gauges then use the right measurement method. The development of our gauges in this matter adheres to national and international standards such as:
- DIN EN ISO 2808
- DIN EN ISO 2178
- DIN EN ISO 2360
- DIN 50981
- BS 5411 (11)
Non-destructive coating thickness measurement on metal substrates
Non-destructive, tactile coating thickness measurement on metal substrates can be roughly divided into two measurement methods:
- Measurement on a ferromagnetic substrate such as iron or steel: The type of substrate and the associated measurement mode usually have the brief designation Fe. The measurement methods utilised here are those that take advantage of magnetic induction. A magnetic field is generated by a permanent magnet or electromagnet and measured with a Hall sensor (electromagnet or permanent magnet possible) or a secondary coil (only electromagnets).
- Measurement on non-ferrous or non-ferromagnetic but electrically conductive substrate such as aluminium, zinc, copper, brass and certain stainless steel types: This type of substrate and the associated measurement mode are designated with NFe. The eddy current method is utilised for this purpose.
QNix® offers its wide assortment of gauges and probes for many fields of application. All conventional measurement methods are used:
- Magnetic induction with electromagnet and measurement with secondary coil (magnetic induction measurement method) – DIN EN ISO 2178
- Magnetic induction with electromagnet and measurement with Hall sensor – DIN EN ISO 2178
- Magnetic induction with permanent magnet and measurement with Hall sensor – DIN EN ISO 2178
- Eddy current method – DIN EN ISO 2360
What base material is available?
The base material of the metal coating base is not always clearly visible or quickly discernible during vehicle assessment, for example. Therefore QNix® gauges automatically use the right measurement method for the job. In the motor vehicle sector, in particular, more and more body parts are made of aluminium. Many users work under time pressure and are unable to check the base material thoroughly before the measurement. QNix® coating thickness gauges help users by identifying what the underlying metal substrate they are dealing with. If a QNix® coating thickness gauge identifies steel or iron (Fe) as the coating base, it then uses the alternating magnetic field method according to DIN EN ISO 2808. If the gauge registers non-ferrous metals (NFe) as the base material, it takes the measurement using the eddy-current method in accordance with DIN EN ISO 2178.
This allows coatings made of non-magnetic but electrically conductive layers such as chromium, zinc or tin on magnetic substrates such as steel or iron (Fe) to be determined. In addition, users can also determine the layer thickness of electrically insulating coatings such as paint or anodic coating on non-ferromagnetic but electrically conductive base materials such as aluminium (NFe).
This includes, for example:
- aluminium (such as in aircraft construction as well as as frame construction and bodywork in motorcycle and car manufacturers)
- stainless steel
- copper (such as in pipe systems)
- zinc (such as hot-dip galvanised coating)
- magnesium
The coating can involve various materials. The QNix® series can measure the thickness of the following sample surfaces non-destructively:
- lacquers
- electroplating
- films
- anti-corrosion coatings
- anodising
- powder coatings
- PTFE (known from the Teflon coating on frying pans, for example)
- fusion coatings (such as enamel)
HEAVY-DUTY CORROSION PROTECTION
Shipbuilding | Offshore | Bridges | Energy distribution | Chemical industry
How QNix® coating thickness gauges focus on accuracy
In measuring technology a measured result is considered accurate if it is both true and precise. Even if you have to deal with coating thickness measurements regularly in your daily professional life, the concepts of trueness, precision and accuracy can be confusing. The following explanation should clarify the conceptual differences.
Trueness
Precision; Synonym: variance
Why is it important to distinguish trueness, precision and accuracy? Very simple: The systematic error of a measuring system (trueness) can be determined and documented through calibration. Trueness can be improved through adjustment. Random error (precision) cannot be improved. In case of poor precision, it is very unlikely that a single measured value is close to the average of many individual measurements. That means, poor precision can only be countered by a greater number of individual measurements, and that is time-consuming for the user.
The QNix® series gauges have a high degree of accuracy. The trueness and precision of each gauge that leaves our facility are tested individually. This makes us a reliable partner when it comes to coating thickness measurement.
The QNix® series can be used for a large variety of coating materials and substrates. Automation Dr. Nix develops and produces all QNix® series in its facility in Germany. The company adheres to the typical "Made in Germany thoroughness". Automation Dr. Nix has internalised this type of mentality. We are pleased that we can make good high-quality products in Germany.
Do you have technical, application-related or product-related questions about coating thickness measurement?
Please continue reading, write us an e-mail or give us a call. We will be happy to offer you some advice: +49 (0)221 91 74 55-0
How abrasion affects the trueness of measured results
Coating thickness gauges are used in some instances in tough environments. What is critical here is that the probe pole or the measuring tip quickly wears. The probe pole in each coating thickness gauge defines the distance between the surface of the coating and the actual sensor system. If the measuring tip is worn, the distance decreases and the trueness of the measurement is no longer completely guaranteed. For this reason, we use rubies as the measuring tip of our gauges and probes. Ruby with its Mohs hardness of 9 is one of the hardest materials ever – only diamonds are harder. In addition, the surface of the ruby is polished to avoid damaging decorative coatings, for example.
When and how should users adjust their coating thickness gauge?
Every coating thickness gauge is subject to a large number of errors that affect the trueness of the measured result. The most important influencing factors are:
- temperature changes
- the material properties of the base substrate,
- the geometry of the measured object.
High-quality coating thickness gauges possess very good temperature compensation. In spite of everything, users should always check the trueness of measuring results in case of strong temperature fluctuations. This can happen, for example, with an uncoated substrate (the reference plate) and a calibration standard (the calibration foil). If you as a user discover unacceptable discrepancies, the gauge should be adjusted.
In most cases the material properties of the substrate can be compensated by adjustment (often called calibration as well). The most common are:
- Zero-point calibration: Standardisation to the uncoated substrate
- One-point calibration: Adjustment with a calibration standard of known thickness
- Multiple-point calibration: Adjustment with several calibration standards of known thickness
Whether the geometry of the measured object has an effect on the measured result (for example, in case of curvatures), you can first check the manufacturer's specifications in the data sheet. In borderline cases or in case of doubt, trueness here must be checked as well using calibration standards on the uncoated substrate and, if necessary, adjusted.
In most cases, with the QNix® measuring technology and the factory calibration individually determined for each probe and stored in the gauge, you can already achieve a high degree of measurement trueness using zero-point calibration (standardization) to the original, uncoated substrate. After the zero-point calibration, you can verify measurement trueness using calibration standards.
Important: To verify or improve the trueness of your coating thickness gauge, only use calibration standards whose tolerances you know and were certified by the manufacturer or a calibration laboratory.
High degree of trueness and precision in a QNix® coating thickness gauge
QNix® products are characterised by a high degree of accuracy. Every coating thickness gauge automatically undergoes individual calibration at the factory. We then test each gauge for trueness and precision in our calibration laboratory and create a test certificate. In this manner we ensure that every gauge that leaves our facility meets the narrowly defined tolerance specifications.
Insight into the QNix® series
The current series of QNix® coating thickness gauges is as diverse as the applications of our customers.
- As a modular apparatus with exchangeable probes with up to a maximum 5,000 µm measurement range and memory capacity of up to 30,000 measured values in up to 250 blocks, the QNix® 8500 has been setting new standards in coating thickness measurement since 2005 with its constant upgrades. The QNix® 8500 can be used in any application where maximum flexibility in measurement and seamless measuring result documentation are indispensable.
This gauge can be used, for example, for quality assurance and documentation of the coating process in heavy-duty corrosion protection as well as in offshore installations, bridges, power poles and shipbuilding. In these fields of application, in particular, every applied layer of the underlying coating system, from electroplating to the top coat, must be documented. Users can save the thickness of each individual layer and the total layer thickness per component or area in individual blocks, export them in an Excel file and document everything conveniently using the PC software QN7.
With the CarCheck System Plus upgrade, motor vehicle experts can also benefit from traceable documentation of measured values.
We are continuously expanding the range of our optional probes, thus emphasising the flexibility of the QNix® 8500. Our range of probes for coating thickness measurement includes standard probes for Fe, NFe or both substrate types (with a measurement range of 2000 µm or 5000 µm), wireless probes for wireless transmission of measured values between portable device and probe, and our thin-layer probe for measurements of thin films and small parts in surface finishing. The QNix® 8500 also offers the possibility of integrating any standard probe or using it with an interchangeable cable.
- The compact and easy to use QNix® 4500 gauge is available with an integrated probe or an optional cable probe, making it the small allrounder in the QNix® series. It can be used flexibly in the measurement range of up to 3000 µm or 5,000 μm on Fe substrates and up to 3,000 μm on NFe substrates. For the sake of simplicity, the QNix® 4500 and QNix® 4200 have no measurement data memory. As a result, the gauge gets by with just one button that simplifies operation significantly. The QNix® 4500 is most often used in tasks where no documentation is needed and the focus is on fast and easy testing of layer thickness.
- For motor vehicle experts the QNix® 1500 is a reliable classic that is impresses because of its robustness and simplicity. Because of its two independent integrated probes for steel and aluminium and three contact points, the gauge can be used in a reliable and versatile manner. If you want to change the substrate, simply reverse the gauge. This lets you know at all times which substrate you are currently measuring. The long-lasting, polished ruby measuring head tip protects the paint of the vehicle and is extremely wear-resistant. The QNix® 1500 M offers additional memory and statistics functionalities. The measurement range of up to 5,000 µm, the simple and quick zero-point calibration without calibration standards (calibration foils) and the very easy and intuitive operation make the QNix® 1500 a reliable tool for many motor vehicle experts.
Position, measure and read: our coating thickness gauges are that simple
The QNix® series focuses on the easy-to-use principle and uncomplicated handling: all QNix® coating thickness gauges are always ready to use immediately. In most applications they get by with just one adjustment (calibration) to the base material.
