2017 Award Nomination
Title of Innovation: PosiTector® RTR-P Replica Tape Reader Nominee(s) DeFelsko Corporation Category: Instrumentation (select one below)
Coatings and Linings Cathodic Protection Materials Design Chemical Treatment
Instrumentation - X Testing Integrity Assessment Other—fill in
Dates of Innovation Development: April, 2014 to April, 2015 Web site: www.defelsko.com/rtr
Summary Description: Surface replicas obtained using TestexTM Tape contain far more information than just peak height as measured by a micrometer. Significant data is available through digital imaging. The patented PosiTector RTR-P uses imaging sensors to measure the Peak Density (Pd) information contained in replica tape in addition to peak height. Advanced models are able to generate 2D/3D images and SDF files of the replicated surface. Black and white 2D and color 3D images are ideal for inclusion into reports and for confirming a consistent blast profile. A high resolution SDF (surface data file) can be imported into third-party rendering software for further examination at a cost far less than interferometric or confocal profiling devices.
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Full Description: (Please provide complete answers to the questions below. Graphs, charts, and photos can be inserted to support the answers.) 1. What is the innovation? Replica tape has been used to measure the profile of abrasive blasted steel since the late 1960's. Compared to other methods, it has the advantages of ruggedness, relatively low start-up cost, good repeatability and the option of retaining a physical replica of the surface being evaluated. This method is widely used and understood.
It is not widely known that surface replicas obtained using Testex Tape contain far more information than just peak height as measured by a micrometer or by our PosiTector RTR-H. Significant data is available through digital imaging. The PosiTector RTR-P uses thickness and imaging sensors to characterize replica tape and generate images and statistics of the original surface. A black and white two dimensional (2D) image is essentially a photograph of the burnished tape. It reveals a pattern of dark and light spots similar to what you might see if you put the replica tape in front of a light source. The bright areas are higher compressed tape (peaks) and dark areas are lower compressed tape (valleys). Peak density is determined by simply counting the bright spots. In addition to producing 2D and 3D images of every replica tape measurement, the PosiTector RTR can also generate an SDF (surface data file) that can be imported into free or purchased third-party rendering software. The result is 3D maps of the blasted steel surface at a cost far less than interferometric or confocal profiling devices.
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2. How does the innovation work? Surface replicas obtained using Testex Tape contain far more information than just peak height as measured by a micrometer. Areas of the tape compressed by the peaks in the profile allow light to pass through, while uncompressed areas block light. The PosiTector RTR-P shines light through the burnished replica tape, and captures the resulting image. From this image, the number of peaks can be calculatedby simply counting the bright spots. The light intensities at each point (pixel) can also be calculated into a height value, using a calibration curve derived by engineers at DeFelsko and Testex. This means that the PosiTector RTR-P can generate high-resolution 3D images of the surface, all from an inexpensive piece of replica tape. After a burnished piece of replica tape is evaluated by the PosiTector RTR-P (in less than 10 seconds), the peak count is instantly displayed on the screen, in addition to a low resolution image of the surface profile (see photo above). The user can also download a high-resolution surface data file (SDF), which can be imported into PosiSoft software to further analyze the surface, and derive values equivalent to a drag stylus, such as Ra, Rq, Rz, Rt, and Wa.
3. Describe the corrosion problem or technological gap that sparked the development of the innovation? How does the innovation improve upon existing methods/technologies to address this corrosion problem or provide a new solution to bridge the technology gap? In 1974 Keane et al. 1 wrote that a surface prepared for painting via blast cleaning could not be completely described by measuring peak-to-valley distance (H) alone. Their paper supported field experience which suggested that there was another important parameter besides H, namely, the number of peaks per unit length (Peak Count - Pc) or peaks per unit area (Peak Density - Pd). Besides increasing bonding surface area, the paper explained that increasing the number of peaks in a defined area increased the angularity of that area. That put more shear adhesion stress on the coating rather than tension (pull-off) stress. This increased coating bond strength for the applied coating as shear values are always higher than tensile values. The applied coating, of course, must wet out 100% of the surface. The below figure is a simplified example of why BOTH peak height AND peak density are important to the understanding of coating performance. The two surfaces have different geometries yet their height measurements are the same. To get a clearer picture of the surface available for bonding, peak count measurements must also be obtained. Furthermore, both measured values make it possible to investigate the increase in surface area resulting from the abrasive blasting process.
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J.D. Keane, J.A. Bruno, and R.E.F. Weaver, Surface Profile for Anti-Corrosion Paints, Publication #74-01, SSPC: The Society for Protective Coatings, Pittsburgh, PA 15222, 1974 3
Pd = 1.5 peaks/mm2
Pd = 3 peaks/mm2 (2x)
Both surfaces have the same measured peak-to-valley height. A second important measurable parameter, peak density, helps explain why coatings bond differently to each surface.
In June of 2005 a significant paper by Roper et.al. 2 reported peak counts could be controlled and, like peak height, affect coating performance. Their work resulted in the creation of ASTM D7127 which was also published that year. The authors recommended that stylus roughness instruments, the best field instrument available at the time, be used in the corrosion industry to provide both critical pieces of profile information -- peak height AND peak density. However, the use of stylus roughness instruments never gained acceptance in the corrosion industry. They are fragile in nature and depend on a precisely calibrated stylus that often extends a distance from the body of the device itself. They can be complex to set up and to operate, and they report a number of roughness parameters that are of limited interest to the coatings industry. Finally, these instruments have a significant initial cost. All these factors likely dissuade potential users. In November 2014, a paper 3 by David Beamish, President of DeFelsko, used the PosiTector RTR-P to reinforce Roper’s findings and explain the innovative jump from one dimension peak count (Pc) measurements obtained from stylus instruments to two dimension peak density (Pd) measurements obtained from the PosiTector RTR-P. Most notably, a strong positive correlation between peak density and adhesion was found, as shown in the figure below from that paper.
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H.J. Roper, R.E.F. Weaver, and J.H. Brandon, The Effect of Peak Count or Surface Roughness on Coating Performance, Journal of Protective Coatings and Linings, June 2005, pp. 52 - 64 3 Replica Tape – Unlocking Hidden Information, Journal of Protective Coatings and Linings, July 2015, 4
Observed peak density versus adhesion strength on 25 steel samples
4. Has the innovation been tested in the laboratory or in the field? If so, please describe any tests or field demonstrations and the results that support the capability and feasibility of the innovation. Yes. The PosiTector RTR-P was developed and extensively tested by DeFelsko, in association with the Testex company (manufacturers of Testex replica tape) in 2014 and 2015. Since its commercial release in April 2015, it has been a strong commercial success. At the upcoming NACE and SSPC conferences, we expect several papers to be presented based upon data generated from PosiTest RTR-P measurements. ASTM D4417, “Standard Test Methods for Field Measurement of Surface Profile of Blast Cleaned Steel” is being revised to include this low-cost field instrumentation, acknowledging the fact that peak density measurements have become more practical. Final balloting and publication is expected in early 2017. SSPC-PA 17, “SSPC-PA 17, Determining Compliance with Steel Profile/Surface Roughness/Peak Count Requirements” has just been opened for revision to include findings from this technology. Balloting on the first draft is also expected in early 2017. In addition, extensive testing and validation of the RTR-P’s measurements has been performed through comparison with existing and accepted technologies.
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The Worcester Polytechnic Institute conducted a comparison of the RTR-P to their scanning laser confocal microscope, a laboratory bench-top machine costing over $50,000. The results from the RTR-P compared closely with that device. The RTR-P was also compared to conventional drag stylus instruments, using the same test panels as used in round robin testing under ASTM D7127 “Measurement of surface roughness of abrasive blast cleaned metal surfaces using a portable stylus instrument.” A direct correlation was exhibited between the published test results and those obtained using the RTRP on the same test panels. 5. How can the innovation be incorporated into existing corrosion prevention and control activities and how does it benefit the industry/industries it serves (i.e., does it provide a cost and/or time savings; improve an inspection, testing, or data collection process; help to extend the service life of assets or corrosion-control systems, etc.)? The PosiTector RTR-P is used to measure peak count during the post-blast inspection, at the same time as salt contamination and blast profile height inspection takes place. If the inspector already uses Testex tape to measure profile height, the PosiTector RTR-P doesn’t involve any additional steps- it measures profile height at the same time it measures peak count and generates an image of the surface. This innovation gives new insight into the relationship between surface profile and adhesion and helps paint formulators and abrasive suppliers better understand the mechanical bonding mechanisms used to hold protective coatings to steel substrates. Major producers have already begun using this instrument and are researching these surface dynamics to provide a custom product for individual customer needs. It allows consultants, engineers, and specifiers to ensure a blast profile maximizes coating adhesion, while also ensuring that it stays consistent. With a more consistent profile and better adhesion, clients can expect better coating performance, and fewer early failures. 6. Is the innovation commercially available? If yes, how long has it been utilized? If not, what is the next step in making the innovation commercially available? What are the challenges, if any, that may affect further development or use of this innovation and how could they be overcome? Yes, The PosiTector RTR-P has been commercially available since April 2015. 7. Are there any patents related to this work? If yes, please provide the patent title, number, and inventor. Yes. Title: Apparatus and method for Characterizing a Replica Tape 6
U.S. Patent Nos. 8,994,933 B2 and 9,207,174 B2 Inventors: Leon Vandervalk, Robert V. Stachnik, James Edward Davis
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