Water Ballast Tanks Success Or Failure
Coatings in water ballast tanks could as easily become a failure as a success. A few important factors should be discussed with yards and owners, preferably before a contract is signed, to make any necessary adjustments and find amicable ways to accept a possible extra cost.
One-coat systems of 200-250 microns DFT are tempting to yards when they consider the saving in manpower and time a second coat represents. But the price for a second coat is always willingly accepted by owners when it is included in the original specification, including proper financing.
Jotun has never had any reports about an owner who has asked for a reduction in a newbuilding price by reducing a two-coat system to a one-coat system, or accepting a discount by reducing the DFT in a water ballast tank.
Jotun have numerous reports, however, on owners who have declined a yard's increase in cost for a two-coat system when the increased costs are unreasonable, or if the owners are confronted with an upfront additional payment.
Two-coat systems are generally more to be recommended. They are safer, as they reduce variations in dry film thickness due to manual application. A two-coat system reduces the risk of porosity in the coating film.
Stripe-coating prior to the first and intermediate coats is important to ensure protection of areas of difficult access. Without stripe-coating, many areas will not be reached by airless spray. Edge corrosion will start undercutting.
Secondary pretreatment is clearly best after blast-cleaning of welds and damaged areas. If this is not permitted and only St 2-3 is allowed for, polishing must be avoided. Polishing is commonly a result of the use of rotating wire brushes. Use disc grinders when possible.
Included in secondary pretreatment is the removal of dirt and water-soluble salts, be they water soluble zinc salts from shopprimers of water soluble welding deposits.
These are the major factors. Should the work procedure or specification disagree with your opinion of what is to be recommended, discuss it. You should diplomatically make your opinions understood. Should your clients disregard your opinions, put your reservations, it is easy for the client to put the blame on the supplier of the materials. It can cost in direct repairs or settlements, it can cost Jotun's reputation in the long term.
We must be responsible when accepting supply to a doubtful specification. It may take courage and create unpleasantness, but in the long run we will have fewer complaints, more satisfied customers, and an improved reputation which again means more positive and profitable business.
