The coating on a vessel is only a fraction of the thickness of the structural steel, and certainly much less than the cost of the steel, but without paint the asset value would rapidly decrease and working life would be short. Therefore, the UK P&I Club has issued a Risk Focus booklet to address how to guard the asset value from corrosion.
Paint can have a profound effect on both running costs and revenue generation. The primary role of a coating is to protect the asset from the environment it has to work in, in order to provide as long a service life as possible Not only does corrosion affect service life, it has a real and detrimental effect on costs to the asset owner in terms of service time, down time, performance levels and ultimately, asset value.
At a glance
- Studies show 41% of coating failures are due to poor specification
- Repairing coatings offshore can be up to 100 times the cost of the initial coating
- Worldwide, $25 billion per annum is spent on marine coatings
- Each year, $2 trillion is spent tackling corrosion
- One tonne of steel rusts every 90 seconds
- Faulty paint is the cause of 3% of failures
One of the biggest areas for coating issues is found in cargo tanks -coating problems can directly affect revenue generation.The cargo carrying spaces on board a vessel primarily require corrosion protection.
For chemical and product tankers that require carriage of high purity cargos, coating the tanks preserves the purity of the cargo by preventing contamination from the steel substrate. Uncoated mild steel tanks will corrode when aqueous and water containing cargoes are carried. These tanks would then be unsuitable for carrying higher purity cargoes such as methanol etc. A good tank lining also speeds up the cleaning process during cargo sequencing.
It is well recognised that as the coating comes towards the end of its lifetime, cargoes move towards the ‘dirty end’ of the spectrum where coating condition is not an issue. However, these cargoes are not as valuable as the high purity ones, so the tanks need to be kept in as good a condition as possible to maintain this higher revenue.
To preserve coating life, there are three clear steps:
- Select the correct coating scheme
- Ensure good surface preparation
- Ensure paint application conforms to the paint specification
Concentrate on the key areas that cause the most pain with regard to coatings:
- Underwater hull
- WBTs
- Cargo tanks and cargo holds
Further details regarding painting operations may be found in the report below
Source: UK P&I Club
