With its scenic seaside vistas and breathtaking beaches, the coastal city of Gladstone is truly a sight to behold. Located in the Central Queensland region of Australia, Gladstone experiences a tropical savannah climate, featuring alternating dry and wet seasons.
According to the Australian Bureau of Meteorology, annual mean temperatures for Gladstone range from approximately 19 to 28 °C (~66–82 °F) with an annual mean rainfall of about 32 inches (81.3 cm). Along with long, hot summers, strong winds are a persistent issue year-round.
These weather conditions were a factor when protective coatings contractor Chemcote Specialty Coatings visited an aluminum refinery in Gladstone in late April 2021. Based in Wollongong, New South Wales, Chemcote specializes in long-term, anti-corrosion solutions for the heavy industrial sector.
Such expertise was needed for this particular project, which was to apply coatings to the refinery’s chemical storage and delivery bund that surrounded a 60,000-liter (15,850.3 gallon) storage tank containing 98% sulfuric acid. A coatings solution was required for the entire 5,380-square-foot (499.8 m2) secondary containment that would prevent potential leaks or spills from the tank’s corrosive contents from deteriorating the concrete substrate and entering the environment.
The asset owner, which wishes to remain unnamed, had requested a Chemco International specification based on successful past performance in chemical storage areas within the facility over the past 20 years. And Chemcote was uniquely situated to satisfy this need due to its status as the approved Australian distributor and applicator of Chemco International’s protective coatings systems. According to Greg Bladowski, project manager for Chemcote, Chemco is the manufacturer of the coatings system while Chemcote is a separate entity.
After consulting with refinery engineers, Chemcote identified a durable Chemco coatings system that involved the use of Damp-crete RH 800, a moisture-tolerant primer designed for freshly laid concrete, and Epo-chem RF 500, a topcoat that offers outstanding resistance to most chemical agents, particularly strong acids. Once this system was selected, Chemcote worked closely with Chemco and updated the coatings manufacturer regularly on new developments.
In so doing, the coatings contractor was able “to showcase the Chemcote product range and the suitability of these products to withstand the harsh environments found within this and other similar facilities,” said Stephen Smith, project supervisor for Chemcote.
A Coatings Time Crunch
As Smith recalled, when his three-person crew began work in April 2021, “existing production areas were heavily deteriorated, and a refinery life extension forced the expansion of process areas to keep up with ever-increasing demands. Most of the construction in the surrounding areas were still incomplete on our arrival.”
While other sections of the refinery were open and operational, the bund area where Chemcote and other contractors operated was a new build with coatings application marking one of the final steps toward completion.
According to Smith, the production schedule couldn’t wait the standard 28-day cure period that concrete normally requires. The fact that this Chemco coating system was ideally suited for freshly laid concrete and required a minimum substrate temperature of 5 °C (41 °F) made it a particularly appealing option to the asset owner.
The Chemcote crew had a tight four-week window to complete their work. Meeting this deadline involved a good deal of pre-planning on the part of both Smith and Bladowski; they needed to formulate approvals and site plans prior to mobilizing to the jobsite.
Once on site, Smith communicated regularly with the asset owner and the general contractor, Youngs Building Construction, to facilitate daily operations. He also participated in morning planning meetings with other subcontractors and provided updates on progress and activities that might impact work schedules.
Bladowski was also present during the initial phase of the project to ensure that there were no teething issues by checking the crew’s compliance with site-specific requirements and verifying the condition of the concrete bund before coatings work could begin.
That work started with the Chemcote crew using a hygrometer to check the moisture content of the seven-day cured concrete. The results showed that it did meet the acceptable 75% equilibrium relative humidity (ERH) level based on the manufacturer’s application and substrate preparation guidelines. Additionally, a check on the concrete’s compressive strength revealed it to be at 25 n/mm2 (3,626 psi), which was within the standard strength range.
Once the concrete’s moisture content and compressive strength had been confirmed, the bund was ready to be prepped. First, the crew used Milwaukee Tool hand grinders to smooth out surface imperfections. Working from the outside in using stiff brooms, the crew then applied an acid/water mix to loosen unsound concrete. Next, all surfaces were thoroughly rinsed using a Kerrick 3,000 psi (20.7 MPa) cold water pressure washer that neutralized the surface prior to coatings application. The overall surface prep goal was to create a rough substrate with an International Concrete Repair Institute (ICRI) Concrete Surface Profile (CSP) of 1–3.
On that prepped surface, the crew applied a coat of the Damp-crete RH 800 primer at an average of 100 microns (3.9 mils) dry film thickness (DFT) using Graco 70:1 airless sprayers for large open areas and UNi-PRO mohair rollers for hard-to-reach areas. While the crew observed environmental conditions for applying the primer that met manufacturer specifications, the tropical savannah climate occasionally reared its unpredictable head.
“There were no humidity restrictions for the primer, provided it was under 35 °C [95 °F],” said Smith. “Due to inclement weather, we exceeded the recoat window after priming the lay-down area. We had to abrade the entire surface area, then blow it down and apply another coat of RH 800 using Graco airless spray guns.” Sectional sanding of the bund that required coating after the overcoat window was exceeded was then carried out, with crew members using cordless sanders with 120-grit sanding discs with built-in vacuum systems to reduce surface dust.
After the RH 800 primer was successfully reapplied, a consolidator tool was used to roll a layer of 220 gm/m2 woven fiberglass matting around the interior bund walls and external curbs. The woven fiberglass compensated for the expansion and contraction of the substrate and coating system. Any remaining cracks and holes in the substrate were repaired with touch-up applications of RH 800.
From there, a topcoat of Epo-chem RF 500 was applied at an average of 250 microns (9.8 mils) DFT using Graco airless sprayers, along with an Atlas Copco 269 CFM diesel compressor, which supplied air to those sprayers. The topcoat formed a durable barrier that provides outstanding protection for the concrete surfaces.
Finally, a 30/60 grade garnet abrasive, used to provide additional non-slip properties, was broadcast into the wet topcoat with a hand-held air-driven mini-blaster. Once surfaces were blown dry to remove excess garnet, another coat of RF 500 was spray applied at an average of 595 microns (23.4 mils) DFT.
Throughout the coatings process, crew members wore personal protective equipment (PPE) that included Tyvek disposable coveralls, MicroGuard disposable boot covers over Oliver waterproof and caustic-resistant work boots, safety gloves, and powered air-purifying respirators (PAPRs). When applying the coatings, the crew complied with local environmental laws as the coatings system was 100% solids with no volatile organic compounds (VOCs). The coating system had the added advantage of being appropriate to use with substrates with up to 90% ambient humidity.
Beating the Heat and Staying Safe
With ambient temperatures in Gladstone reaching above 30 °C (86 °F) throughout the duration of the project — not to mention mid-day temperatures exceeding 40 °C (104 °F) — the Chemcote crew made sure that appropriate storage solutions were utilized to keep the temperature of the coatings under 30 °C prior to mixing. They also eschewed the mid-day heat and typically applied coatings between 5–11 a.m. and again between 4–8 p.m., working 12-hour shifts six days a week.
Additional measures were also taken to beat the heat. “Thermal gun testing of the concrete surface temperatures were regularly carried out, with cool fresh water being directly applied to the substrate to bring the temperature down when required,” Smith said. “The pot life of the product also had to be monitored when higher temperatures were experienced, with smaller batch mixing and shorter application windows carried out to accommodate [excessive heat].”
Another issue plaguing the crew was dust caused by several simultaneous operations throughout the facility, including other trades working within the bund area alongside Chemcote. The spread of this dust was aided by the excessive wind that’s a fact of life in Gladstone. However, Smith said that “this was allayed with the periodic wetting down of adjacent areas to reduce dust [along with] regular blowing down and sweeping of our work area and pre-planning of alternate work in another area of the bund when simultaneous operations were unavailable.”
Because the crew worked in close proximity to a sulfuric acid tank, special safety precautions were a must. For starters, crew members were fit tested for PAPRs prior to the commencement of the project. Along with wearing appropriate PPE, each crew member had a monitor to assess for airborne gases and possible ingress of toxic chemicals through the skin.
Moreover, they each had a personal supply of Diphoterine solution, an emergency rinsing solution used as a precautionary measure for the treatment of chemical spills and splashes. Bladowski said that the product came in fit-for-purpose dispensing containers small enough to be carried on the belts of crew members.
Last but not least, all work areas were cordoned off with appropriate safety signage, and walkways within the bund area were sectioned off to avoid excessive contamination to the substrate.
Approximately four weeks after Chemcote commenced with its coatings work, the customer performed a final inspection and signed off on its satisfactory completion in late May 2021. Smith said that Chemcote’s ability to meet its deadline allowed the facility to move closer toward its goal of completing the newly created concrete bund.
For its part, Chemcote was able to meet the challenge to provide a long-term coatings solution for a facility containing acidic chemicals in an aggressive environment.
While the heat was often sweltering and the wind and dust considerable, the crew was able to overcome the elements to safely deliver a result that will keep the facility’s bund in good condition for years to come.