CORROCOAT South Africa report an interesting case study from its USA partners when asked to perform a corrosion assessment for a client on a 2 year old, four storey sulphuric acid building.
The building houses a sulphuric acid generator on a petrochemical plant. Due to incorrect material selection, the process piping leaked acid throughout the building. This caused significant deterioration to the galvanized structure and concrete. The concrete was previously lined with a competitor’s concrete coating designed for short-term exposure in secondary containments. Beneath the leaking areas and around the concrete were pitted to depths of up to 100mm deep.
Shortly after reviewing Corrocoat USA’s corrosion assessment report, the client hired the team to supply and apply its Plasmet AR3 lining system. The lining system would refurbish the surface and protect against continual immersion. Some work was completed using pre-coated fiberglass sheets. This took place whilst the building was running, and then applied directly at a later stage to the prepared concrete. Throughout this stage of the project, the client addressed the root causes of their corrosion problems.
The surface was prepared using a wet abrasive blast unit, combined with utilisation of a salt remover. This was followed by a high pH cleaning agent to alkalinize the surface. The concreate pH was then tested to ensure compliance to Corrocoat USA’s own standards. Plasmet ECP (Epoxy Concrete Primer) was applied at 152 – 254 microns wet film thickness (WFT). Plasmet ECP penetrates into the concrete protecting subsequent coats from latent moisture, while fortifying the concrete at the surface.
Prior to installation of the new pumps in the building, the 10m x 0.6m x 0.6m high pump bases were poured using Corrocoat’s Epoxy Polymer Concrete (EPC). The EPC cures to provide a 1 380 bar compression strength and 124 bar tensile strength. It can be coated the following day, saving time while increasing reliability.
Pits on the surface were filled with Corrocoat Zip E Screed, a glass flake reinforced epoxy coating enhanced with a proprietary blend of fillers. This allows for resurfacing to direct liquids towards the sump – an important aspect of the customer’s engineering team.
Once the screed was sufficiently hardened, Plasmet AR3 was applied at 1 200 -1 500 microns. The coating was applied in two to three coats, mixing in an aggregate for non-skid in the high traffic areas. As we have seen in many other applications, the Plasmet AR3 is unaffected in the presence of all concentrations of Sulphuric Acid – it was the ideal solution for this project.
At one stage of the project, the team had to leave the site for several weeks. This was whilst the Corrocoat Zip E Screed was down in an area without the topcoat. During their absence, there were repeated releases of the 40% sulphuric acid onto the Zip E Screed and the coating held up well. It was easily swept blasted and over coated after being submerged for days.
On the galvanized steel, the team prepared the surface using a mixture of pressure washing with their 350 bar, 17 ℓ/min pressure washer. This was in conjunction with the power tools, to prepare the portions of steel that were showing signs of corrosion. They primed with Plasmet ZF and the nuts and bolts were stripe coated using Corrofill E. The structure was then coated using the AR3, applied at 812 – 1 000 micron.
