CROSS OUT CORROSION A cross section of pipe that was successfully coated with Corrocoats Corroglass coating system
Last month, anti-corrosion coatings manufacturer Corrocoat announced it has been awarded a contract to protect 300 new pipe spools of various dimensions by a multinational energy client.
The company say its Corroglass 600 series was the coating system selected for this project, as it offered the best long-term corrosion protection on the floating production, storage and offloading units.
With pipe diameters between 50 mm and 300 mm, a number of coating strategies were employed including Corrocoat sister company Corroserves’ in-house pipe-blasting and pipe-coating technology, pipe-rolling and a carefully controlled flood and drain technique.
Used primarily on small bore pipes of complicated geometry, the flood and drain technique allows coating to be applied by its trained technicians, into areas which would otherwise not be accessible.
Notably, this technique has been successfully used for lining pipes with Corrocoat materials for over 40 years.
As part of the quality assurance requirements, the client requested that a pipe, lined by flood and drain should be cut and assessed after coating, to show the notable coverage, which was advised would be achieved using this application method.
A pipe containing two bends and a tee piece were supplied by the client for the assessment.
The internal surfaces of the pipe were first abrasive blasted and then coated with Polyglass VE Pipegrade, using the flood and drain method.
Application was carried out four times, allowing the coating to gel between coats and ensuring that the coverage was sufficient.
The spool was allowed to cure for seven days prior to being split along its length, using an angle grinder.
As expected, the client noted there was a small amount of mechanical damage at the edge of the cuts, but away from these areas the coating was found to be uniform and intact.
Dry film thickness readings were found to be a minimum of 1.260 µm with an average of 1.436 µm and a standard deviation of 135.63 µm.
Readings were taken every 150 mm along the length of the pipe, which was also spark tested at 17 000 kV alternating current, and no defects were found.
Adhesion was then tested in accordance with American Society for Testing and Materials D4541.
The surface of the coating and the adhesion dollies were abraded with particle 60 sandpaper.
The test dollies were attached using the same batch of Polyglass VE Pipegrade as the adhesive, then tested after 24 hours using a hydraulic adhesion test.
The results of the test were remarkable, as the coated test spool had an average adhesion value of greater than 20 MPa, which was the limit for the test equipment.
In conclusion, the coating thickness, integrity and adhesion was found to be excellent along the length of the spool piece, validating the method of application, as would be expected for this high performance Corrocoat lining.