01362 691484
info@corrolesseastern.co.uk

CHP Container Protective Coatings, Ireland

THE PROBLEM

The existing protective coatings on the steel CHP container had broken down extensively on the units roof, with corrosion of the structure commencing. During our survey we identified flexing in the roof structure and poor adhesion of the coating across the entire structure.

It appeared from our survey that minimal or no preparation had been undertaken prior to the application of the existing coating system, with minimal surface profile visible on the areas where coating was removed during survey.

THE SOLUTION

We proposed that all existing protective coatings be removed and a new coating system applied. We proposed the application of Rustoleum Noxyde given the materials flexibility would be able to accommodate any flexing in the roof structure.

In accordance with ISO 12944 Rustoleum Noxyde is tested to give over 15 years until first maintenance in the most demanding C5M environment, meaning that in this less demanding environment even longer should be expected.

We implemented a rigorous testing and inspection regime to ensure the longest possible service life of the new protective coatings for our client.

Initially the existing coatings were checked for soluble salt contamination using the Brestle test method. These were found to be higher than permitted and a washing regime was implemented to remove these.

If left in place prior to abrasive blasting these can be forced further into the steel substrate by the blasting process which can lead to osmotic blistering of the new protective coatings.

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As requested the client fully encapsulated the container to enable both dust control using a filtered dust extractor and also when painting works were to take place the introduction of heating and dehumidification to ensure the correct climatic conditions for coating application.

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Prior to abrasive blasting extensive protection works of areas not to be prepared and coated were undertaken.

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The blast media itself was tested for chloride contamination to again prevent the forcing of chlorides into the steels surface profile.

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The blasting equipment was tested for efficiency using a needle pressure gauge and the cleanliness of the blasting air tested using the blotter method. Abrasive blasting is most efficient when the pressure is 100 psi or greater at the nozzle. The blotter test checks for oil contamination of the blast air which if present would contaminate the substrate and prevent adhesion of the new protective coating system

All existing coatings were then removed and the steel prepared to SA2.5 as per ISO8501-1.

The client had raised concerns that the reason for the poor adhesion of the previous protective coatings was contamination of the steel prior to painting. To verify whether this was the case all surfaces were checked for oil contamination using a UV Blacklight

To verify the chloride levels present on the steel further soluble salt tests were conducted post preparation using the Chlor Test method. The benefit of this test method compared to the Brestle method is that there are no temperature constraints. By contrast the Brestle method is intended to be conducted at 20 degrees centigrade.

All surfaces were vacuumed clean and a surface cleanliness test conducted to ensure the effectiveness using the dust tape method. If surfaces are not cleaned sufficiently this will prevent the proper adhesion of the new protective coating system.

The surface profile of the steel was tested and recorded using a surface profile needle gauge. Sufficient surface profile is paramount to ensuring the optimum adhesion of the new protective coating system.

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The blast standard was maintained using dehumidification equipment, although strictly this was not required as Rustoleum Noxyde can be applied to water jetted  and hand prepared surfaces.

Prior to and during protective coating application works the climatic conditions were tested and recorded to ensure compliance with the manufacturers recommendations.

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Awkward areas and angles, edges etc were stripe coated by the application of Rustoleum Noxyde by method of brush and roller. This was followed by the application of the first coat at a practical coverage rate of 0.4Kg/m2 for optimum corrosion protection.

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The accuracy of this application was tested using frequent wet film thickness readings during application and dry film thickness readings once this first coat had dried.

A second coat of Rustoleum Noxyde was then applied at the same thickness as the first coat, but in a contrasting colour to aid identification as per best protective coating practice.

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To ensure a seamless and pin hole free finish a low voltage spark test was conducted using the wet sponge method, with any pin holes or ‘holidays’ detected marked and made good using the same material applied by brush.

Finally to achieve the desired RAL Colour Rustoleum Metal Cladding Top Coat was applied by method of airless spray. Once dry the extensive masking was removed prior to final sign off with the client.