Coatings - Onboard Maintenance
Water, weather, wear – these are three problems the vessel is exposed to and they directly influence the lifetime of the paint systems which should protect your ship against corrosion. Ships today have smaller operational crews and faster turnaround in ports than ever before. Consequently, the time that can be devoted to maintenance of shipboard coatings has been reduced drastically. Paint systems applied during newbuilding period of the vessel are, in general, high quality paints. However, paint systems will deteriorate and, therefore, coatings need maintenance – in sake of safety, operational efficiency or just for cosmetic reasons. After all, the ship is also your home.
The protective coatings must be periodically maintained like engines and mechanic equipment. Preventive maintenance will reduce the extent of corrosion and also the interval between the maintenance jobs. But, is it at all possible to carry out rational and economical coating maintenance with the limited resources available on board ships today? Yes, it is, but there are few steps which should be followed.
Step 1 - Planning
Before you start the shipboard maintenance, you have to identify the defects in the paint system and find out what exactly needs to be done, which tools you will need and if you have correct quality and quantity of paint on board and other things. The weather conditions and ship operations shall also be taken into account.
Step 2 – Safet
If you can do your job in a safe way, you protect yourself against accidents and the results of the work carried out will improve. Is your safety equipment in good condition? Use a boiler suit, safety boots, wear gloves, ear protection and mask, goggles and, of course, a helmet. Use the correct protection equipment for the right job. When you work in confined spaces, make sure there is proper ventilation and lighting, and make sure that the pre-treatment and application equipment is in good condition
Step 3 – Surface Preparation
Removal of oil, grease, and fat is done by an emulsifier since wiping with rags soaked into solvent redistributes rather than removes fatty substances. This preparation is very important since oil, grease, fat and salts cannot effectively be removed by mechanical cleaning. After this, fresh water washing has to be done in order to remove salts. When the surface is dry, corrosion products, thick paint layers and loosely adhering paint can then be removed.
This can best be done by mechanical tool like a scraper, which is suitable to remove thick rust layers and paint but should be followed by a wire brushing or disc grinding. Other tools could be the needle gun, which is good in removing hard rust scale or heavily rusted layers of paint; this tool tends to make indentations in steel. A good wire brush is ideal for removing rust, but be aware that too much brushing will polish the surface and poor adhesion of the paint will be the result.
The disc sander is also a suitable tool for feathering edges and sanding intact coatings. The edges of the repaired areas should be feathered smooth. The surrounding intact coating should also be sounded in order to secure adhesion. For smaller or difficult areas this can be done by hand, bigger areas – with a sander; note that the sanding may be omitted for acrylic coatings. But make sure that the correct type of tool is used for the right job.
Step 4 – Paint Preparation
Before you start to handle or use any paint, learn all that is worth knowing about this product and the correct and safe use of it. Look into your maintenance manual and specification, and also in the product data and safety datasheets. Ensure that the paint is stored under correct and safe conditions. Make sure that the paint locker is well ventilated. Check the specification and select the right products. Use the correct cure agents and thinners and use them in the correct quantity.
Step 5 – Paint Application
Then, on the dry and dust-free surface the first coat of the repair system can be applied. You have to stir paint with the mixer before you can apply it. The paint should have a completely uniform color with no sediments. Then, stir for an extra 30 seconds. Note that wrong mixing will result in poor performance. Primers are ideally applied by brush and, if possible, using a minimum of two coats within the same working day in order to obtain enough paint protection after the pre-treatment.
Unless spray application equipment is on board, the best way is to apply paint by brush. The brushing action assist the paint to penetrate the surface and, beside spray application, is the only suitable method to apply primers. The film thickness which you apply per coat by brush is approximately 40 microns. This means that you need more than two coats to protect the pre-treated steel. For the correct number of coats you have to consult the specifications in your maintenance manual.
The most common paint application tool on board ships is probably the roller, but it should not be. Roller application leaves an uneven form and numerous thin spots. Corrosion will start in these weak areas and continue on the paint system. Sooner or later, heavy rust can be observed. When enough primer coats have been used, the top coat can be applied. Correct mixing of the top coat is also necessary. When you mix the paint in a correct way, the application gives a much better result.
After the final application, close the paint drums in a right way, and store them again properly in the paint locker. Clean your application tools using the correct method so that you can use them again next time. A lot of work, but with satisfying result; perhaps troublesome, but necessary.
Blistering is a result of the solvent entrapment. Painting on top of a bit of rust or when you apply film in a tool thin film gives bad results. And, paint application over thicker layers can result in lifting, flacking, or cracking.
Keep Maintenance Simple
Keep intact coatings free from dirt and salt. Maintenance by cleaning is also a worthwhile activity. The removal of oil, grease, salt and other contamination will prolong the lifetime of the coatings. Preventive maintenance will utilize man-hours and equipment more economically. Do the maintenance operations thoroughly and remember the right sequence. When you follow these simple steps, you work and live safely on board the well-maintained vessel.
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