Now part of the Fortune Global 500, Ecopetrol S.A. is the primary petroleum company in Colombia. It is among the 25 largest global petroleum companies and is one of just four principal providers in Latin America. Thus, when the perimeters of two internal welding rings on a naphtha storage tank were found to have metal loss, the oil company needed an urgent solution.
Colombia-based coatings contractor Imantt Solutions had worked with Ecopetrol at its flagship Cartagena refinery for nearly a decade. Once the oil company realized the extent of the problem in 2018 during maintenance work, that prior relationship with the contractor proved critical in moving the process along.
“Imantt had been working with Ecopetrol since 2010 solving different kinds of corrosion problems in their facilities,” said Mario Candela, owner and CEO at Imantt. “We visited the Cartagena refinery every month speaking about how to implement modified epoxy in their tanks.”
The contractor’s first priority at Cartagena was to understand the extent of the problem on the carbon steel tank. From there, they could determine the optimal solution.
“Defects and structural heterogeneities led to welded joint deterioration,” Candela explained. “When they are in aggressive areas with exposure to water, chlorides, sulfides, and high operating pressure, the conditions are favorable for localized corrosion to develop.” According to the contractor, mill scale had rusted away on the tank, and pitting corrosion was visible to the naked eye.
Imantt Solutions is the exclusive Colombian distributor for performance coatings and repair compounds manufacturer MCOR, whose thixotropic MCOR 3115 material, or mClad mFill, was specified to restore the tank’s 1,506.9 sq. ft. (140.0 m2) of perimeter weld seams. The two-component, high-strength epoxy paste is described by the manufacturer as having non-sag and quick-setting properties. The epoxy paste is modified with fibers and ceramics and can be used for general industrial grade repairs, resurfacing, and as patch filler for metal.
“With this product, we seek to recover the lost metal, protect effectively under immersion, and avoid possible faults by movements,” said Candela, who added that the product offers excellent elongation and tension properties.
Once the coating solution was agreed upon by the contractor and client, Imantt’s crew got right to work at the Cartagena refinery in November 2018. First on the agenda was personal protective equipment (PPE) for their eight crew members and the head metallurgical engineer within the confined space. According to the contractor, PPE gear on this project — supplied by providers including MSA and Colombia’s Zubi-Ola — consisted of safety glasses, gloves, hard hats, breathable particle protection coveralls, particulate respirators, harnesses, and shock-absorbing lanyards.
To ensure the material’s adhesion properties and the substrate’s corrosion protection, surface preparation was an essential first step. Using scaffolding as needed for access, crew members blasted the internal tank weld seams to achieve the NACE No. 1/Society for Protective Coatings (SSPC) Surface Preparation (SP) 5: White Metal Blast Cleaning standard. This standard means that when viewed without magnification, the surface should be free of all visible oil, grease, dust, dirt, mill scale, rust, coating, oxides, corrosion products, and other foreign matter.
With the surface prepared, the crew next had to ensure that environmental conditions were suitable for coating. The ambient temperature range for MCOR 3115 application is between 27 °C and 34 °C (80.6–93.2 °F), while relative humidity (RH) levels should be between 68 and 78 percent. While the hot and humid conditions on Colombia’s coast are usually within that range, instruments including DeFelsko’s PosiTector DPM and Lutron’s TM-936 thermometer were used each day to measure the levels. The tank’s surface also had to be at least 3 °C, or ~5 °F, higher than the dew point temperature to avoid condensation, so the Positector DPM helped monitor those conditions, as well.
Once conditions were deemed appropriate, crew members advanced to the application phase. Working section by section, the initial application priority was to prepare the MCOR 3115 material, which is supplied in two containers. “We mixed a complete unit in the proportions supplied in a flat mixing board,” Candela said. “We mixed thoroughly with a spatula next, and then applied the mixture with pointed trowels.” The material, which combines into a grey color with a matte finish, was trowel-applied in one coat at an average dry film thickness (DFT) of 40 mils (1,016.0 microns).
The eight crew members took a divide-and-conquer approach to application. Some mixed, others applied the material, and a third group performed continual tests to ensure the application met both industry and manufacturer standards. Using an MCOR thickness gage and DeFelsko’s PosiTector 6000, crew members verified the desired DFT throughout the tank. They also performed spot bond strength tests using DeFelsko’s PosiTest AT pull-off adhesion testers, in accordance with the ASTM D4541 standard. As a finishing touch, crew members measured film continuity throughout the tank’s seams in accordance with the ASTM D5162 standard for holiday testing on metallic substrates.
Eight Is Enough
According to the contractor, test results showed no bond failure or detachment of the MCOR 3115 material, and thickness measurements were continually within the desired range. And after just eight days, the eight crew members successfully completed their assignment! There were occasional delays due to drizzles of rain but nothing that cost significant working hours.
“A final inspection was carried out by the reliability department of Ecopetrol,” Candela said. “They expressed their satisfaction with the application and confirmed its compliance. Once the quality control tests were completed, the application and presentation of the epoxy coatings were approved by Ecopetrol.”
After the Imantt crew finished its job, a separate contractor arrived to install a final topcoat over the newly coated seams — just for aesthetic purposes, to tie in the color of the seams with the remainder of the now tan-colored tank. By the end of November, the tank was restored both functionally and aesthetically, allowing the Colombian oil major to head into 2019 and beyond with full confidence that its flagship refinery can operate as needed.
“Eight Is Enough” is best known as the title of a once successful television series, but it can certainly be applied to the crew on this job, as well. Judging from the looks of the tank, eight is great!