Oxifree – A guarantee seal

Rust, the corrosive effect of water and oxygen on iron and its alloys, such as steel, is well documented. When the water is contaminated with salt, such as with seawater, or when dissimilar metals are in contact with each other, the effect is even faster. Take one of these elements away from the metal and the rusting of the metal stops though. Take them both away from the metal and you can be quite certain that corrosion will not take place.

Traditionally paint has been used. But paint degrades and is difficult to remove. For example when nuts and bolts on painted flanges are required to be loosened or removed, a needle gun is needed to chip the paint off the metal. This action can damage the metal and produce polluting waste.

Offshore WIND was recently invited by Oxifree to their Dutch office in IJmuiden to look at their new coating which is easy to apply, easy to remove, and is recyclable.

Function

Oxifree is an organic polymeric resin coating that can be sprayed from a hand held gun connected by a heated hose to an Oxifree Polymelt application machine. The resin is heated to 175°C in the application machine and pumped through the hose to the gun from where it is sprayed over the metal area to be coated.

The metal can have a previous coating of paint or primer, but should have any loose debris removed and have been cleaned of grease and oil using a normal detergent prior to application. The substrate also needs to be dry for the coating to be applied effectively. After a few minutes it has cooled to the ambient temperature where it becomes a solid seal against water and air. All waste excess material from the application process can be put back into the Oxifree Polymelt unit for application elsewhere.

The makers of Oxifree have included active organic corrosion inhibitors which, together with a passive outer polymer coating, ensure a protective barrier against all types of corrosion and contamination. This active organic corrosion inhibitor, being oil-based, also acts as a lubricant which enables the material to be applied to certain rotating machinery (typically low rpm), such as bearing housings on a free spinning drive-shaft. The seal can prevent not only moisture but also caked salt, resulting from a marine environment, and dust and grit from entering the bearing, prolonging the life of the bearing and reducing downtime.

The makers have not released too many details of the resin compound, which is protected by a patent pending, but the coatings have been tested to prove that they are non-harmful, it containing less than 0.05% volatile organic compounds (VOC’s) making it an extremely environmentally friendly solution.

Removal

Removing the coating to allow a flanged pipe section to be replaced, or bolted equipment removed, is easy. Using a recommended cutting tool the coating can be removed in part or whole. Provided the removed section is not heavily contaminated, it can then be placed in the application unit and melted for re-use.

Application

The applications for Oxifree coatings in the offshore wind industry are obvious. Anywhere in the splash zone on the transition piece, or inside the tower or turbine housing where the high humidity salt air can rapidly cause corrosion in this marine environment. Attachments, such as sections of the J tube and the ladder outside on the TP, the railings, cranes, light fittings and fall protection equipment on the gallery are all items that are usually bolted to the structure and not welded. This is due to a possible future requirement to be replaced when damaged or to be opened up for inspection. These are all items that are ideal for an application of Oxifree coating.

A single application of the coating has been tested by the ATSM B117 Sea Salt Spray Test (over 11,600 hours with no corrosion) to last over 20 years in situ.

The weights of the units when empty are 50kg (Polymelt 50) and 27kg (Polymelt 12). The larger machine can be operated from a 220/240VAC single phase supply taking a maximum of 11.5KW with a 30Amp breaker fitted electric supply. The smaller machine takes a maximum of 2.5KW and can be operated from either a 110VAC or a 220/240VAC supply.

The demonstration of the application and removal of the Oxifree coating that Offshore WIND saw was very complete. The only question remaining for us was whether the resin floated in water or not. This was another test that the Oxifree team were willing to prove. Nicholas Kail, the CEO of the Oxifree’s Dutch operation, filled a bucket with water from the tap and dropped some of the waste coating into the water – it sinks. QED!

Dick Hill