For more than half a century, municipal councils, as well as industrial and mining companies have invested billions of dollars in equipment and infrastructure to process waste water and sewage. Corrosion of this infrastructure, and in some cases the subsequent leakage, costs industry in excess of $1 billion each year, according to Rhino Linings Australasia (RLA).
The main assets that are impacted by corrosion in waste water treatment plants (WWTP) are the pipelines, storage tanks, clarifier ponds and sewage channels.
One method of refurbishment of these assets is to carry out surface repairs and then apply protective coatings. These coatings must be strong, flexible and resistant to chemical attack.
RLA special projects engineer, Dennis Baker, said corrosion particularly affects the submerged parts of structures in WWTPs.
“Special consideration has to be given when coating structures in sewage treatment plants; one of the more corrosive by-products of sewage is hydrogen sulphide gas,” he said.
Baker said one type of coating from RLA that is ideally suited for waste water treatment is spray applied Polyurea. The company has been working with this material since the early 1990s and locally manufactures a range of consistent formulations which are suitable for a variety applications.
The Rhino Linings Pure Polyurea comes as a two-part solution that is mixed under high temperature and pressure (3000 psi at 65ºC) in a specially designed spray apparatus.
“When applied, the excellent chemical cross linking produces a dense but flexible surface. The high density makes the coating almost impervious to abrasion, water and chemicals,” he said.
“We need to educate the engineering market place about the benefits and cost effectiveness of this versatile and adaptable material.”
Whereas epoxies and paints form a solid rigid shell, the flexibility of polyurea coatings allows them to move with the expansion and contraction of the underlying structure as temperatures change.