Coating Surface Test Instruments
Among our test instruments for coating and surface evaluation are COATING THICKNESS METERS, SURFACE ROUGHNESS TESTERS, GLOSS METERS, COLOR READERS, COLOR DIFFERENCE METER, METALLURGICAL MICROSCOPES, INVERTED METALLOGRAPHIC MICROSCOPE. Our main focus is on NON-DESTRUCTIVE TEST METHODS. We carry high quality brands such as SADTand MITECH.
A large percentage of all surfaces around us are coated. Coatings serve many purposes including good appearance, protection and giving products certain desired functionality such as water repelling, enhanced friction, wear and abrasion resistance….etc. Therefore it is of vital importance to be capable to measure, test and evaluate the properties and quality of coatings and surfaces of products. Coatings can be broadly categorized into two main groups if thicknesses are taken into consideration: THICK FILM and THIN FILM COATINGS.
To download catalog for our SADT brand metrology and test equipment, please CLICK HERE. In this catalog you will find some of these instruments for the evaluation of surfaces and coatings.
Some of the instruments and techniques used for such purposes are:
COATING THICKNESS METER : Different types of coatings require different types of coating testers. A basic understanding of the various techniques is thus essential for the user to choose the right equipment. In the Magnetic Induction Method of coating thickness measurement we measure nonmagnetic coatings over ferrous substrates and magnetic coatings over nonmagnetic substrates. The probe is positioned on the sample and the linear distance between the probe tip that contacts the surface and the base substrate is measured. Inside the measurement probe is a coil that generates a changing magnetic field. When the probe is placed on the sample, the magnetic flux density of this field is altered by the thickness of a magnetic coating or the presence of a magnetic substrate. The change in magnetic inductance is measured by a secondary coil on the probe. The output of the secondary coil is transferred to a microprocessor, where it’s shown as a coating thickness measurement on the digital display. This quick test is suitable for liquid or powder coatings, platings such as chrome, zinc, cadmium or phosphate over steel or iron substrates. Coatings such as paint or powder thicker than 0.1 mm are suitable for this method. The magnetic induction method is not well suited for nickel over steel coatings because of nickel’s partial magnetic property. Phase-sensitive Eddy current method is more suitable for these coatings. Another type of coating where the magnetic induction method is prone to failure is zinc galvanized steel. The probe will read a thickness equal to the total thickness. Newer model instruments are capable of self-calibration by detecting the substrate material through the coating. This is of course very helpful when a bare substrate is not available or when the substrate material is unknown. Cheaper equipment versions require however calibration of the instrument on a bare and uncoated substrate. The Eddy Current Method of coating thickness measurement measures nonconductive coatings on nonferrous conductive substrates, nonferrous conductive coatings on nonconductive substrates and some nonferrous metal coatings on nonferrous metals. It is similar to the magnetic inductive method previously mentioned containing a coil and similar probes. The coil in the Eddy current method has the dual function of excitation and measurement. This probe coil is driven by a high-frequency oscillator to generate an alternating high-frequency field. When placed near a metallic conductor, eddy currents are generated in the conductor. Impedance change takes place in the probe coil. The distance between the probe coil and the conductive substrate material determines the amount of impedance change, which can be measured, correlated to a coating thickness and displayed in the form of a digital reading. Applications include liquid or powder coating on aluminum and nonmagnetic stainless steel, and anodize over aluminum. This method’s reliability depends on the part’s geometry and the coating’s thickness. The substrate needs to be known prior to taking readings. Eddy current probes shouldn’t be used for measuring nonmagnetic coatings over magnetic substrates such as steel and nickel over aluminum substrates. If users must measure coatings over magnetic or nonferrous conductive substrates they will be best served with a dual magnetic induction/Eddy current gage that automatically recognizes the substrate. A third method, called the Coulometric method of coating thickness measurement, is a destructive testing method that has many important functions. Measuring the duplex nickel coatings in the automotive industry is one of it major applications. In the coulometric method, the weight of an area of known size on a metallic coating is determined through localized anodic stripping of the coating. The mass-per-unit area of the coating thickness is then calculated. This measurement on the coating is made using an electrolysis cell, which is filled with an electrolyte specifically selected to strip the particular coating. A constant current runs through the test cell, and since the coating material serves as the anode, it gets deplated. The current density and the surface area are constant, and thus the coating thickness is proportional to the time it takes to strip and take off the coating. This method is very useful for measuring electrically conductive coatings on a conductive substrate. The Coulometric method can also be used for determining the coating thickness of multiple layers on a sample. For example, the thickness of nickel and copper can be measured on a part with a top coating of nickel and an intermediate copper coating on a steel substrate. Another example of a multilayer coating is chrome over nickel over copper on top of a plastic substrate. Coulometric test method is popular in electroplating plants with a small number of random samples. Yet a fourth method is the Beta Backscatter Method for measuring coating thicknesses. A beta-emitting isotope irradiates a test sample with beta particles. A beam of beta particles is directed through an aperture onto the coated component, and a proportion of these particles are backscattered as expected from the coating through the aperture to penetrate the thin window of a Geiger Muller tube. The gas in the Geiger Muller tube ionizes, causing a momentary discharge across the tube electrodes. The discharge which is in the form of a pulse is counted and translated to a coating thickness. Materials with high atomic numbers backscatter the beta particles more. For a sample with copper as a substrate and a gold coating of 40 microns thick, the beta particles are scattered by both the substrate and the coating material. If the gold coating thickness increases, the backscatter rate also increases. The change in the rate of particles scattered is therefore a measure of the coating thickness. Applications that are suitable for the beta backscatter method are those where the atomic number of the coating and substrate differ by 20 percent. These include gold, silver or tin on electronic components, coatings on machine tools, decorative platings on plumbing fixtures, vapor-deposited coatings on electronic components, ceramics and glass, organic coatings such as oil or lubricant over metals. The beta backscatter method is useful for thicker coatings and for substrate & coating combinations where magnetic induction or Eddy current methods won’t work. Changes in alloys affect the beta backscatter method, and different isotopes and multiple calibrations might be required to compensate. An example would be tin/lead over copper, or tin over phosphorous/bronze well known in printed circuit boards and contact pins, and in these cases the changes in alloys would be better measured with the more expensive X-ray fluorescence method. The X-ray fluorescence method for measuring coating thickness is a noncontact method that allows the measurement of very thin multilayer alloy coatings on small and complex parts. Parts are exposed to X-radiation. A collimator focuses the X-rays onto an exactly defined area of the test specimen. This X-radiation causes characteristic X-ray emission (i.e., fluorescence) from both the coating and the substrate materials of the test specimen. This characteristic X-ray emission is detected with an energy dispersive detector. Using the appropriate electronics, it’s possible to register only the X-ray emission from the coating material or substrate. It’s also possible to selectively detect a specific coating when intermediate layers are present. This technique is widely used on printed circuit boards, jewelry and optical components. The X-ray fluorescence is not suitable for organic coatings. The measured coating’s thickness should not exceed 0.5-0.8 mils. However, unlike the beta backscatter method, X-ray fluorescence can measure coatings with similar atomic numbers (for example nickel over copper). As previously mentioned, different alloys affect an instrument’s calibration. Analyzing base material and coating’s thickness are critical for ensuring precision readings. Todays systems and software programs reduce the need for multiple calibrations without sacrificing quality. Finally it is worth mentioning that there are gages that can operate in several of the above mentioned modes. Some have detachable probes for flexibility in use. Many of these modern instruments do offer statistical analysis capabilities for process control and minimal calibration requirements even if used on differently shaped surfaces or different materials.
SURFACE ROUGHNESS TESTERS : Surface roughness is quantified by the deviations in the direction of the normal vector of a surface from its ideal form. If these deviations are large, the surface is considered rough; if they are small, the surface is considered smooth. Commercially available instruments called SURFACE PROFILOMETERS are used to measure and record surface roughness. One of the commonly used instruments features a diamond stylus traveling along a straight line over the surface. The recording instruments are able to compensate for any surface waviness and indicate only roughness. Surface roughness can be observed through a.) Interferometry and b.) Optical microscopy, scanning-electron microscopy, laser or atomic-force microscopy (AFM). Microscopy techniques are especially useful for imaging very smooth surfaces for which features cannot be captured by less sensitive instruments. Stereoscopic photographs are useful for 3D views of surfaces and can be used to measure surface roughness. 3D surface measurements can be performed by three methods. Light from an optical-interference microscope shines against a reflective surface and records the interference fringes resulting from the incident and reflected waves. Laser profilometers are used to measure surfaces through either interferometric techniques or by moving an objective lens to maintain a constant focal length over a surface. The motion of the lens is then a measure of the surface. Lastly, the third method, namely the atomic-force microscope, is used for measuring extremely smooth surfaces on the atomic scale. In other words with this equipment even atoms on the surface can be distinguished. This sophisticated and relatively expensive equipment scans areas of less than 100 micron square on specimen surfaces.
GLOSS METERS, COLOR READERS, COLOR DIFFERENCE METER : A GLOSSMETERmeasures the specular reflection gloss of a surface. A measure of gloss is obtained by projecting a light beam with fixed intensity and angle onto a surface and measuring the reflected amount at an equal but opposite angle. Glossmeters are used on a variety of materials such as paint, ceramics, paper, metal and plastic product surfaces. Measuring gloss can serve companies in assuring quality of their products. Good manufacturing practices require consistency in processes and this includes consistent surface finish and appearance. Gloss measurements are carried out at a number of different geometries. This depends on the surface material. For example metals have high levels of reflection and therefore the angular dependence is less as compared to non-metals such as coatings and plastics where angular dependence is higher due to diffuse scattering and absorption. Illumination source and observation reception angles configuration allows measurement over a small range of the overall reflection angle. The measurement results of a glossmeter are related to the amount of reflected light from a black glass standard with a defined refractive index. The ratio of the reflected light to the incident light for the test specimen, compared to the ratio for the gloss standard, is recorded as gloss units (GU). Measurement angle refers to the angle between the incident and reflected light. Three measurement angles (20°, 60°, and 85°) are used for the majority of industrial coatings.
The angle is selected based on the anticipated gloss range and the following actions are taken depending on the measurement:
Gloss Range..........60° Value.......Action
High Gloss............>70 GU..........If measurement exceeds 70 GU, change test setup to 20° to optimize measurement accuracy.
Medium Gloss........10 - 70 GU
Low Gloss.............<10 GU..........If measurement is less than 10 GU, change test setup to 85° to optimize measurement accuracy.
Three types of instruments are available commercially: 60° single angle instruments, a double-angle type that combines 20° and 60° and a triple-angle type that combines 20°, 60° and 85°. Two additional angles are used for other materials, the angle of 45° is specified for the measurement of ceramics, films, textiles and anodized aluminum, while the measurement angle 75° is specified for paper and printed materials. A COLOR READER or also referred to as COLORIMETER is a device that measures the absorbance of particular wavelengths of light by a specific solution. Colorimeters are most commonly used to determine the concentration of a known solute in a given solution by the application of the Beer-Lambert law, which states that the concentration of a solute is proportional to the absorbance. Our portable color readers can also be used on plastic, painting, platings, textiles, printing, dye making, food such as butter, french fries, coffee, baked products and tomatoes….etc. They can be used by amateurs who don’t have professional knowledge on colors. Since there are many types of color readers, the applications are endless. In quality control they are used mainly to insure samples fall within color tolerances set by the user. To give you an example, there are handheld tomato colorimeters which use an USDA approved index to measure and grade the color of processed tomato products. Yet another example are handheld coffee colorimeters specifically designed to measure the color of whole green beans, roasted beans, and roasted coffee using industry standard measurements. Our COLOR DIFFERENCE METERS display directly color difference by E*ab, L*a*b, CIE_L*a*b, CIE_L*c*h. Standard deviation is within E*ab0.2 They work on any color and testing takes only seconds of time.
METALLURGICAL MICROSCOPES and INVERTED METALLOGRAPHIC MICROSCOPE : Metallurgical microscope is usually an optical microscope, but differs from others in the method of the specimen illumination. Metals are opaque substances and therefore they must be illuminated by frontal lighting. Therefore the source of light is located within the microscope tube. Installed in the tube is a plain glass reflector. Typical magnifications of metallurgical microscopes are in the x50 – x1000 range. Bright field illumination is used for producing images with bright background and dark non-flat structure features such as pores, edges and etched grain boundaries. Dark field illumination is used for producing images with dark background and bright non-flat structure features such as pores, edges, and etched grain boundaries. Polarized light is used for viewing metals with non-cubic crystalline structure such as magnesium, alpha-titanium and zinc, responding to cross-polarized light. Polarized light is produced by a polarizer which is located before the illuminator and analyzer and placed before the eyepiece. A Nomarsky prism is used for differential interference contrast system which makes it possible to observe features not visible in bright field. INVERTED METALLOGRAPHIC MICROSCOPES have their light source and condenser on the top, above the stage pointing down, while the objectives and turret are below the stage pointing up. Inverted microscopes are useful for observing features at the bottom of a large container under more natural conditions than on a glass slide, as is the case with a conventional microscope. Inverted microscopes are used in metallurgical applications where polished samples can be placed on top of the stage and viewed from underneath using reflecting objectives and also in micromanipulation applications where space above the specimen is required for manipulator mechanisms and the microtools they hold.
Here is a brief summary of some of our test instruments for the evaluation of surfaces and coatings. You can download details of these from the product catalog links provided above.
Surface Roughness Tester SADT RoughScan : This is a portable, battery-powered instrument for checking surface roughness with the measured values displayed on a digital readout. The instrument is easy to use and can be used in the lab, manufacturing environments, in shops, and wherever surface roughness testing is required.
SADT GT SERIES Gloss Meters : GT series gloss meters are designed and manufactured according to international standards ISO2813, ASTMD523 and DIN67530. The technical parameters conform to JJG696-2002. The GT45 gloss meter is especially designed for measuring plastic films and ceramics, small areas and curved surfaces.
SADT GMS/GM60 SERIES Gloss Meters : These glossmeters are designed and manufactured according to international standards ISO2813, ISO7668, ASTM D523, ASTM D2457. The technical parameters also conform to JJG696-2002. Our GM Series gloss meters are well suited to measure painting, coating, plastic, ceramics, leather products, paper, printed materials, floor coverings…etc. It has an appealing and user friendly design, three - angle gloss data is displayed simultaneously, large memory for measurement data, latest bluetooth function and removable memory card to transmit data conveniently, special gloss software to analyze data output, low battery and memory-full indicator. Through Internal bluetooth module and USB interface, GM gloss meters can transfer data to PC or exported to printer via printing interface. Using optional SD cards memory can be extended as much as needed.
Precise Color Reader SADT SC 80 : This color reader is mostly used on plastics, paintings,, platings, textiles & costumes, printed products and in the dye manufacturing industries. It is capable to perform color analysis. The 2.4” color screen and portable design offers comfortable use. Three kinds of light sources for user selection, SCI and SCE mode switch and metamerism analysis satisfy your test needs under different work conditions. Tolerance setting, auto -judge color difference values and color deviation functions make you determine the color easily even if you don’t have any professional knowledge on colors. Using professional color analysis software users can perform the color data analysis and observe color differences on the output diagrams. Optional mini printer enables users to print out the color data on site.
Portable Color Difference Meter SADT SC 20 : This portable color difference meter is widely used in quality control of plastic and printing products. It is used to capture color efficiently and accurately. Easy to operate, displays color difference by E*ab, L*a*b, CIE_L*a*b, CIE_L*c*h., standard deviation within E*ab0.2, it can be connected to computer through the USB expansion interface for inspection by software.
Metallurgical Microscope SADT SM500 : It is a self-contained portable metallurgical microscope ideally suited for metallographic evaluation of metals in laboratory or in situ. Portable design and unique magnetic stand, the SM500 can be attached directly against the surface of ferrous metals at any angle, flatness, curvature and surface complexity for non-destructive examination. The SADT SM500 can also be used with digital camera or CCD image processing system to download metallurgical images to PC for data transfer, analysis, storage and printout. It is basically a portable metallurgical laboratory, with on-site sample preparation, microscope, camera and no need for AC power supply in the field. Natural colors without the need for changing light by dimming the LED lighting provides the best image observed at any time. This instrument has optional accessories including additional stand for small samples, digital camera adapter with eyepiece, CCD with interface, eyepiece 5x/10x/15x/16x, objective 4x/5x/20x/25x/40x/100x, mini grinder, electrolytic polisher, a set of wheel heads, polishing cloth wheel, replica film, filter (green, blue, yellow), bulb.
Portable Metallurgraphic Microscope SADT Model SM-3 : This instrument offers a special magnetic base, fixing the unit firmly on the work pieces, it is suitable for large-scale roll test and direct observation, no cutting and sampling needed, LED lighting, uniform color temperature, no heating, forward / backward and left / right moving mechanism, convenient for adjustment of the inspection point, adapter for connecting digital cameras and observing the recordings directly on PC. Optional accessories are similar to the SADT SM500 model. For details, please download product catalog from the link above.
Metallurgical Microscope SADT Model XJP-6A : This metalloscope can be easily used in factories, schools, scientific research institutions for identifying and analyzing the microstructure of all kinds of metals and alloys. It is the ideal tool for testing metal materials, verifying the quality of castings and analyzing metallographic structure of the metalized materials.
Inverted Metallographic Microscope SADT Model SM400 : The design makes possible inspecting grains of metallurgical samples. Easy installation at the production line and easy to carry. The SM400 is suitable for colleges and factories. An adapter for attaching digital camera to the trinocular tube is also available. This mode needs MI of the metallographic image printing with fixed sizes. We have a selection of CCD adapters for computer print-out with standard magnification and over 60% observation view.
Inverted Metallographic Microscope SADT Model SD300M : Infinite focusing optics provides high resolution images. Long distance viewing objective, 20 mm wide field of view, three -plate mechanical stage accepting almost any sample size, heavy loads and allowing nondestructive microscope examination of large components. The three-plate structure provides the microscope stability and durability. The optics provides high NA and long viewing distance, delivering bright, high-resolution images. The new optical coating of SD300M is dust and damp proof.
For details and other similar equipment, please visit our equipment website: http://www.sourceindustrialsupply.com