This article looks at paint protection and how offshore hydraulic power units are specially painted to combat corrosion and other weathering conditions typically found at sea.
In order for the paint to protect the power unit against the elements, it is crucial that it goes through the correct stages of preparation and the paint contains the right chemical mix to make sure it does the job it is tasked with.
The international standard ISO12944 concerns the corrosion protection of paints and is the standard adhered to with regards to the coverage of steel built power units by protective paint systems.
Selecting the right paint
To ensure the correct paint for weather protection is used, several factors need to be taken into account, these include:
Environmental conditions – The first thing to look at when deciding on the composition of the paint is the environment where it will be used. So, looking at an oil rig for example, where anything from sea storms to salt water could affect the application, along with moisture where bacteria can manifest itself on the paint surface and eat into the paint itself.
Regular contact with UV rays and temperature fluctuations are other factors that can be taken into account when looking at operating conditions.
The type of surface that is to be painted – Although the majority of applications are built using steel, aluminium is another strong and lightweight metal so this needs to be taken into account when judging the thickness of the paint needed.
Another important area to look at is the durability of the paint finish and how long it will last before it needs its first refresh. ISO12944 covers this and includes a range of three time frames to categorise paint durability:-
· Low – L = 2 to 5 years
· Medium – M = 5 to 15 years
· High – H = More than 15 years
Surface preparation ready for painting
To ensure the paint adheres to the metal surface of the power unit and remains pliable, the correct steps should be taken when preparing for the painting process.
Surfaces can either be cleaned using an abrasive blasting process or by hand. With abrasive blasting there are several levels of cleaning from light to thorough which ensures all particles are removed leaving a perfectly smooth surface. Hand cleaning is normally carried out by a power tool and with standard or thorough cleaning options.
The paint used also has to be able to resist varying temperatures when the unit is in operation, which will help lengthen the life and quality of the paint. Depending on the type of pigments and binder used, paints can vary greatly in the way they handle excess heat. Silicates and silicones work best when dealing with temperatures over 120 degrees centigrade while also maintaining good low temperature performance. Alkyds and bitumen struggle with intense heat and cold and are best in the 0-100 degrees range. When temperatures get over 400 degrees then aluminium pigment is the only compound that will stand up to these sorts of temperatures.
So, in conclusion when looking to paint a hydraulic power unit it is imperative that the environment, operating conditions and working temperatures are factored into the equation; as well as careful monitoring of the paint finish once the unit is operational to ensure it is durable and lasts the duration.