Paint and Powder Coatings

Paint coatings and powder varnish are frequently used for surface protection. To ensure their functional capabilities, coating thickness and other material properties must be exactly right. Measurement devices from FISCHER allow precise determination of the thickness of paint and powder coatings. The correct measurement technology for reliable coating thickness measurement according to SSPC-PA2.

Paint and powder coatings

Application notes

Duplex Measurement of Lacquer/Zn/Fe for Steel Roofing Systems from BUDMAT®

Roofs are exposed to very harsh weather conditions over many years. To avoid corrosion and guarantee the longevity of steel sheet roofing, the coating of the steel must be of the highest quality. The coating structure is typically built up of three layers of lacquer over a basic zinc coating.

The norm PN-EN 508 – 1.2010 defines the minimum requirement of 275 g/m² zinc coating for such roof coverings. On top of the galvanization there are different types of lacquers available for use, which, together, determine the coating’s final scratch resistance.

Steel sheet roofing materials coated in gloss or matte polyester typically have inner lacquer layers measuring between 27-38 µm. They are considered “thin-layered coatings” and are generally covered by a written guarantee of 10 years.

However, the most highly recommended types have “thick-layered coatings” with an inner lacquer layer 50 µm thick, which gives the steel sheets greater resistance to corrosion and mechanical damage. These high-quality products, such as those provided by the Polish manufacturer BUDMAT®, can be warranted for 30 years.

A characteristic of these sheets is their increased resistance to the kinds of frictional strain to which a roof is often subjected, such as frozen snow, or during assembly. The surface layer contains polymeror ceramic grain which prevents surface scatching.

During the manufacturing process the coated steel sheets are measured with the PHASCOPE® PMP10 DUPLEX. This instrument uses two different electro-magnetic measurement methods to determine the thickness of the paint and zinc layers in a single measurement process and displays the results separately: The magnetic induction method is used for measuring the overall thickness of the paint and zinc on top of the ferrous base material, whereas the phase-sensitive eddy current method is employed for measuring just the zinc coating, irrespective of overlying paint layers. The thickness of the paint layer is calculated automatically as the difference between these two results.

Figure 1: Principle of duplex measurement

Duplex measurements are taken from each production batch and automatically recorded from the host computer – a total quality philosophy. A quality certificate is provided with each delivery.

Because the PHASCOPE® PMP10 DUPLEX instruments are designed for mobile use, it is also possible to test the coating quality of pre-existing roofs.

Figure 2: PHASCOPE® PMP10 DUPLEX 

30-year guarantees can only be provided on steel roofing systems produced according to a high-tech, quality-based manufacturing philosophy. But that requires continuous, vigilant monitoring of the thicknesses of zinc and lacquer coatings on the steel sheet. Because of its ability to perform duplex measurements of different types of coating materials, the instrument ideally suited for this challenge is the handheld PHASCOPE® PMP10 DUPLEX. For further information please contact your local partner for FISCHER products.

Application Note prepared in cooperation with BUDMAT – one of the leading manufacturers of steel roofs and facades, gutter systems and construction profiles. For further info:

www.budmat.pl

Measuring Post Cure Powder Coating Thickness

Powder coating is a popular finish used for functional and decorative purposes on products ranging from outdoor machinery to household items. Measuring the thickness of applied powder coating is a critical requirement for custom coaters and those performing incoming inspection of finished goods. FISCHER instruments utilising the magnetic induction and eddy current methods are the instruments of choice for powder coating thickness measurement.

Powder Coating is applied globally to everything from lawn and garden equipment to furniture, appliance, and automotive components. The thickness of the powder coating applied determines how long the part will last, the part’s appearance and even in some cases the part’s colour. Proper measurement of the thickness therefore is critical.

In today’s competitive climate it is extremely important for anyone applying a coating to adhere to the thickness specification. Monitoring powder coating thickness with a FISCHER hand held coating thickness gauge will ensure this and also potentially save tens of thousands of Euro in costs. Table 1 shows how using a FISCHER instrument can provide cost savings based on annual powder purchases.

Film Thickness Reduction

Cost Savings based on

annual Powder Purchases (€/year)

10,000 €

50,000 €

250,000 €

1,000,000 €

1.00 µm

133

667

3,333

13,333

2.00 µm

267

1,333

6,667

26,667

3.00 µm

400

2,000

10,000

40,000

4.00 µm

533

2,667

13,333

53,333

5.00 µm

667

3,333

16,667

66,667

6.00 µm

800

4,000

20,000

80,000

7.00 µm

933

4,667

23,333

93,333

8.00 µm

1,067

5,333

26,667

106,667

9.00 µm

1,200

6,000

30,000

120,000

10.00 µm

1,333

6,667

33,333

133,333

Table 1: This table reflects the cost savings based on a customer baseline of approx.75 µm. Increments of 1 µm used to demonstrate savings at the smallest measurable level.

Note in Table 1 that increments such as 1µm if measured and controlled properly can provide a significant reduction in costs thus making the custom coater more competitive.

However, only instruments with superior repeatability precision allow for the reliable measurement to this level. Likewise, utilising certified foils to adjust and verify gauge accuracy, something that comes included with the scope of supply of FISCHER instruments vs. non-precise shims will provide the trueness necessary to monitor and adjust a powder coating line properly.

Fig. 1: The DUALSCOPE® MP0R is quick and easy to use yet extremely repeatable. Patented conductivity compensation allow for measurements on various non-ferrous alloys without time-consuming onsite calibration on the actual substrate material

Because powder coating is applied to such diverse parts, selecting the most appropriate instrument and probe is highly important. FISCHER offers a wide selection of instruments and probes starting with small, handy and robust DUALSCOPE® MP0 and MP0R pocket instruments up to the flexible FMP family with numerous interchangeable high-precision probes for the most demanding measurement tasks.

Your local contact person for FISCHER products is happy to assist you in selecting the instrument and probe best suited for your measurement application.

Measuring Protective Coatings in Accordance with SSPC-PA2

Coating thickness measurement is of growing importance in the paint and corrosion protection industry, as is conformance to regulations and standards like SSPC-PA2, a specification that describes procedures to measure the thickness of a dry film (DFT).

As the useful life expectancies for structures such as bridges, ships, pipelines and water tanks have increased, detailed inspections during or after the paint application process have become the norm. SSPC-PA2 provides a uniform way for industrial painting contractors, facility owners and third party inspectors to evaluate these coating projects.

According to SSPC-PA2, a gauge measurement is a single instrument reading, spot measurements are typically the mean of three gauge measurements within a 4 cm (1.5 inch) diameter circle, and area results may comprise the mean of five spot measurements. The frequency of measurements is determined by the size of the structure: If less than 300 square feet (~28 m²), a measurement is taken every 100 square feet (~10 m²). If the structure is between 300 and 1000 square feet (~28 and 100 m²), one arbitrarily selects three random test areas of 100 square feet (~10 m²) and measures.

Fig. 1: Coating Thickness measurement with DUALSCOPE® FMP100

All FISCHER handheld gauges comply with SSPC-PA2. Even the entry level MP0 Series quickly calculates spot mean values. Standard units such as the MP0R have the built in specification to automatically sequence spot mean values while simultaneously monitoring the minimum and maximum readings. In addition, the user is alerted if spot measurements are less than 80% or more than 120% of the specified thickness. In the case of the DUALSCOPE® FMP100, a complete inspection plan with images can be created to guide the user to the location of each measurement.

Selecting the appropriate probe for the application greatly enhances adherence to tolerances, and FISCHER offers various models of gauges, either with integrated probes or gauges able to accommodate multiple separate probes designed for specific measurement challenges.

Your local contact person for FISCHER products will gladly assist you in selecting a suitable handheld coating thickness instrument from the MP0/MP0R or FMP Series for measuring in accordance with SSPC-PA2. FISCHER is a contributor to the Society of Protective Coatings (SSPC) and a member of the SSPC-PA2 committee.

Automated coating thickness measurement in production facilities

More and more often adherence to a specification for the coating thickness of a product is directly monitored in the production facility. This reduces the risk for failure and enables the process to be adjusted in a timely manner. The prerequisite for such an application is a reliable measurement instrument that allows communication with control and monitoring units in the production facility.

To control and if necessary adjust a manufacturing process it is optimal to monitor the process itself and provide direct feedback to regulate the process. For a coating process with tight tolerances regarding the layer thickness this means to measure the coating thickness right after applying the coat. Such process monitoring is an ideal task for the FISCHERSCOPE® MMS® PC2. Coating thicknesses at different positions can be measured simultaneously with up to eight probes.

A key feature for automated process control is the communication between all technical units involved. In industrial manufacturing plants control and monitoring normally take place via a PLC.

The FISCHERSCOPE® MMS® PC2 has USB, LAN and serial communication interfaces as standard, in addition it can be equipped with a digital I/O module which allows remote control of the unit from a PLC.

Fig.1: Schematic layout of automated coating thickness measurement with FISCHERSCOPE® MMS® PC2

The readings of the probes are presented on a TFT display with a good read-out capability. Direct operation of the unit takes place via an integrated touch screen or with an external keyboard and/or mouse. Microsoft Windows CE is used as the operating system, a familiar user interface from many PC programs. The software of the instrument is multilingual and is capable to generate reports in CSV and ASCII format.

Additionally, tolerance limits can be defined for each probe individually, either for parts sorting or just to indicate violation of the tolerance limit using a signal lamp and/or acoustic alarm.

For automated coating thickness measurement in a production facility FISCHER provides a suitable solution with the FISCHERSCOPE® MMS® PC2, connected via modern communication interfaces to a PLC. Up to 8 probes can be controlled, selected according to application needs out of the wide variety of FISCHER probes. Ask your local FISCHER representative for further information.