CoatingsPro Magazine

MAY 2017

CoatingsPro offers an in-depth look at coatings based on case studies, successful business operation, new products, industry news, and the safe and profitable use of coatings and equipment.

Issue link:

Contents of this Issue


Page 69 of 84

COATINGSPRO MAY 2017 69 e laboratory investigation consisted of microscopic examination, visual inspection, solvent resistance testing, and spectroscopic analysis. During the visual and microscopic examination, a Keyene VHX-500 digital microscope with 200X power was used. e findings with this micro- scope showed a total of seven layers of coatings instead of three on some of the samples provided. Some of the samples showed a total of 1.0–5.0 mils (25.4‒127.0 microns) dry film thickness in the inorganic zinc silicate primer coat. Other samples showed evidence of the polyurethane used as a primer instead of zinc silicate. ey also showed evidence of painted-over rust and mill scale. In the solvent testing, most samples showed a high color transfer, and the coatings were removed using the average of five double rubs. e infrared spectroscopic analysis was performed using a Mattson Galaxy model 3020 Fourier infrared spectrom- eter. e sample revealed signs of miss mixing of the two-part coatings systems, which means that the coating system never cured properly. On-Site Observations On site, we were able to observe the application of the coatings. It's not always the case that the coatings are still being applied while the failure analysis is being completed, but in this case, due to the results of these tests, we paid close attention. ere were several observations of note: e contractor did not store nor mix the protective coatings according to the manufacturer's recommendations. First, the coatings were stored in shipping containers and makeshift storage shelters with no environmental controls. We took ambient conditions in these storage containers and obtained readings in the upper 100s °F (37.8 °C). e manufacturer recommends that these coatings be stored at 70 °F (21.1 °C). We also monitored the mixing of the plural component coatings and found on many occasions that the contractors were eyeballing the converter and not using legible mixing cups. Nor were they using whole kits of the two-part coating. All 196,850 feet (60 km) of pipe were rejected. It was decided by the client to move forward by hiring a locally approved contractor inside the country to blast to bare metal and apply one coat of inorganic zinc silicate primer, one coat of organic epoxy followed by one coat of organic polyurethane. is was an economic decision; if this pipe was sent to the country where it was fabricated and coated, it would have set the project back six months. Also, it was in the client's best interest to use a local contractor so we could monitor the abrasive blasting and coating with the use of qualified NACE inspectors that would provide traceability. e pipe was successfully completed per spec. Stuck With Substandard is plant suffered a great number of defects, such as the improperly converted coatings. By not properly mixing the coatings, the plant looked like it was 25 years old and caused a lot of metal sectional loss throughout the plant. Turnkey projects are conve- nient, but without the proper oversight, planning, quality control, and good painting practices in place, catastrophic problems can occur in the future. Protective coatings are essential to The plant's location on the coast offered a hot and humid environment. Also because of the plant itself, there were industrial fallout materials, such as sulfurs and chlorides, that contributed to the failures. Delaminated paint chips were gathered from various locations to take back to a laboratory for further analysis. Holidays, pinholes, and delamination were also noted throughout the plant during the visual inspection. Power Plant Coatings

Articles in this issue

Archives of this issue

view archives of CoatingsPro Magazine - MAY 2017