Inspection Paint coatings

In order to prevent corrosion loss, it is very important to inspect the coating condition inside the ballast tank of ship, such as oil tankers, LNG ships and cargo ships. The current inspection standard defines that the ratio of paint defect surface area in the total surface is visually inspected every two or three years periodically. However, the current visual inspection has some problems, such as the dangerous and dark environment for inspectors, the inaccurate evaluation result depending on the inspector s skill and the time consuming and heavy labor required in order to inspect all the hundreds of tank compartments. In order to overcome these issues,... 

Type interns extendable shelf-life items for which successive re-inspection dates can be established when the items or materials have a continued usability as determined by examination based upon criteria that have been agreed upon. Examples of Type 11 items include paints, coatings and inks. 

Methylene chloride is the active ingredient in many formulations of paint removers including industrial paint and commercial furniture strippers, home paint removers, and products used for aircraft maintenance. The chemical has a unique ability to penetrate, blister, and lift a wide variety of paint coatings. Formulations of the chemical are used extensively in both flow-over and immersion (dip) tanks in furniture refinishing operations. For the maintenance of military and commercial aircraft, a methylene chloride-based product is often required to inspect the surface for damage. 

Coatings (e.g. paints) applied to metal surfaces can be extremely effective in containing the corrosion of the substrate in many environments. This is particularly true for steel in natural environments. However, no freshly applied coating is entirely free from defects and so there will always be small areas which are exposed directly to the corrosive environment. It is possible to reduce, but not eliminate, these defects by paying attention to workmanship. In practice, it becomes increasingly expensive to achieve fewer and fewer defects because of the need for high grade inspection, and the detection and repair of individual defects. 

Figures 19.62 and 19.63 were taken at the time of investigation into a failure of 1001 of steel which should have been coated with a nearly maintenance-free system. Zinc metal spray and four coats of paint were specified but, for reasons of economy, special measures for inspection were not taken. Within months of erection areas were flaking off where millscale had not been removed (Fig. 19.62) and other areas were blistering. Figure...

Thermal transmission testing is an excellent way of detecting various types of anomalies such as surface corrosion under paint before the corrosion becomes visually evident. Thin, single-layer structures, such as aircraft skin panels, can be inspected for surface and subsurface discontinuities. This test is simple and inexpensive, although materials with poor heat-transfer properties are difficult to test, and the joint must be accessible from both sides. For nonmetallic materials, the defect diameter must be on the order of 4 times its depth below the surface to obtain a reliable thermal indication. For metals, the defect diameter must be approximately 8 times its depth. Some bright surfaces such as bare copper and aluminum do not emit sufficient infrared radiation and may require a darkening coating on their surface. 

Determination of R does not require that the current and potential signal be correlated. However, if measurements are made at different times, they should be made with similar working electrodes and similar exposure conditions. R values have been used to assess the degradation of organically coated metals. In these studies, R data appeared to correlate with the film resistance (impedance magnitude at low frequency) values determined from EIS (145), or with visual inspection of painted samples subject to various cabinet exposures (146). 

From a practical point of view, the attainment of the specified dry film thickness is important. In many cases, a minimum thickness must be achieved or protection will fail in a short period. This aspect demands skill in application and close inspection and control. For metallic zinc paints, the thickness would normally be of the order of 60-100/im, for anticorrosive pigmented paints, together with top coats, 100-200 //m, and for inert barrier types 150-300/im. For special environments or projects, these thicknesses may be varied but it should not be presumed that protection will always be improved or be more effective over a longer period of time by increasing the film thickness. 

Uses Antimicrobial, preservative, stabilizer, slimicide for use in latexes, emulsion paint, aq. slurries, adhesives, tape Joint compds., o/w emulsions, paper coatings, pesticides, water-based inks, hides and skins USDA approved for paints used in federally inspected plants and packing adhesives having min. contact with meat or poultry food prods. food pkg. adhesives, paper food-contact slimicide Features Inhibitor of bacteria, yeast, and fungi heat-stable, low corrosivity no formaldehyde released... 

Before a works painting or metal spraying contract for steelwork is awarded, the workshops concerned should be inspected by qualified personnel. It is essential that some check is made to ensure that the necessary facilities and equipment for carrying out all the terms of the order or specification are available. Cleanliness of the painting areas and order in the paint store usually indicate the seriousness with which works personnel take protective-coating operations. 

Built in 1959, the dike at Delfzijl was painted green (epoxy coating) to match the grass. The wall protects the town against flooding by the sea. An inspection made in 1991 showed the zinc coating to be still 80-120 xm thick. No rust had appeared after 32 years. 

Any paint job, even if properly done, does not last forever. Within the first 6 months or year after application, spots, inadvertent misses, or weak spots in the coating system can be detected by simple visual inspection. A thorough inspection and repair should be done at this time. 

Unlike coatings made from thermoplastic powders which require only a visual inspection to see whether the coating is satisfactory, thermosetting powder coatings require additional examination to determine whether the coating has achieved its full physical properties. Simple mechanical tests may be used, as is the practice with conventional paint finishes, but, particularly for epoxy powder coatings, it is normal to use chemical resistance as a criterion for suitability. A common method is to swab the coating continuously for 30 seconds with a cotton wool pad soaked in methyl isobutyl ketone. Any deterioration of... 

Final inspection is a must. There are available a wide range of inspection instruments for determining the thickness of each coat as well as the final total paint thickness. These include various magnetic, eddy current, and destructive thickness gauges. 

Over a period of time the paint film will break down and deteriorate as a result of the environment. Scheduled inspections are recommended to determine the extent and rate of breakdown of the coating. Localized areas of failure should be spot-repaired before large-scale deterioration of the coating takes place. 

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