The Bulk Out Loading Bin was suffering from coating breakdown and corrosion – particularly on the bin lid. A new coating protective coating solution was required.
During our site survey we identified that part of the cause of the failure of the existing coatings was that the original mill scale layer that is present on hot rolled steel had never been removed prior to protective coating application.
Mill scale is a poorly adhered mineral layer that is present on hot rolled steel when it leaves the mill. Correct coating practice states that this must be removed prior to application of any protective coatings. Most typically this is undertaken by method of grit blasting. If mill scale is not removed, over time the bond between this and the steel will break, resulting in subsequent failure of any protective coating system applied.
Therefore initially all of the existing protective coatings and mill scale present we removed by method of grit blasting, preparing the steel to SA2.5.
Ensuring the surfaces were clean
To ensure all surfaces were thoroughly clean the bin was high pressure washed with the inclusion of Denso Holdtight. This product helps to prevent flash rusting from occurring as well as removing any soluble salts that may be present.
Soluble salts if left in place can cause premature coating failure through osmotic blistering as a result of the hygroscopic action of salts drawing moisture through the coating film.
Following preparation and cleaning all seams were sealed using a polyurethane jointing to ensure the structure was water tight in order to protect the grain stored in the bin.
A stripe coat of Rustoleum Noxyde was applied by method of brush and roller, to ensure full film build on the numerous angles and edges. Noxyde has excellent edge retention, but we still applied a stripe coat as per best protective coating practice.
Two full coats of Rustoleum noxyde were then applied by method of airless spray at a practical coverage rate of 0.5Kg/m2, to achieve the recommended wet film thickness required for optimum corrosion protection.
One of the reasons that Rustoleum Noxyde was selected for this project is that once it cures it forms an elastomeric waterproofing membrane that can elongate in excess of 200%, as well as offering excellent corrosion protection.
Another benefit of this protective coating system is that the overspray falls as ‘dry spray’, reducing the risk of overspray damage to surrounding assets. This makes the material very suitable for external protective coating applications.