Painting and coating process and wastes

Material inputs for painting are primarily paints and solvents. Solvents are used in the paints to carry the pigment and binder to the surface and for cleaning the paint equipment. Paints contain toxic pigments such as chromium, titanium dioxide, lead, copper, and tributyltin compounds. The organic solvents contained in marine paints and used for thinning and cleaning are also likely to contain toluene, ethyl benzene, xylene, methyl ethyl ketone, ethylene glycol, «-hexane, and acetone.

Painting wastes are believed to be the largest category of hazardous wastes produced in a shipyard. In a typical shipyard it may account for more than half of the hazardous wastes produced. This may include leftover paint, overspray, paint that is no longer usable, rags, and other materials contaminated with paint. In many cases the amount of paint can be reduced through the use of improved equipment, alternative coatings, and good operating practices. Equipment cleaning also generates hazardous waste in the form of solvents, thinners, and acids. Painting activity involves significant air emissions. Volatile organic compounds and hazardous pollutants result from painting operations that are of concern (Vardar, 2004).

The nature of shipbuilding and repair requires several types of paints to be used for a variety of applications. Paint types range from water-based coatings to high-performance epoxy coatings. Antifouling paints are used to prevent the growth of marine organisms. Copper-based and tributyltin (TBT)-based paints are widely used as antifouling paints, though TBT may only be used on vessels longer than 25 m and with regulatory authority approval. Most of these toxic agents are heavy metals or organometallic compounds, such as cuprous oxide, lead oxide, and tributyltin compounds (Celebi and Vardar, 2006).

VOCs belong to a special category of air pollutants that can adversely affect human health. Industrial operations are important sources of VOCs and there are various technologies that can reduce VOC emissions from these industrial processes (Celebi and Vardar, 2008). Organic solvents are useful to dissolve and disperse lubricants, oils, waxes, paints, varnishes, rubber and so on and are widely used in many industrial processes. Most of them are also recognized as extremely hazardous chemicals and some of them might cause Alzheimer's disease, leu-koencephalopathy, multiple sclerosis, neurobehavioral disorders, and so on. Solvent vapors comprised of VOCs and HAPs are a significant pollutant output of cleaning and degreasing operations. Both halogenated and nonhalogenated solvents are used and mixtures of different solvents are common. Typical cleaning and degreasing solvents include mineral spirits, aromatic hydrocarbons (e.g., xylenes, toluene), aliphatic hydrocarbons, ketones, esters, alcohols, glycol ethers, phenols, turpentine, and various halogenated solvents (Celebi and Vardar, 2006).

Another contaminant type can be named as volatile organic compounds (VOCs) that belong to a special category of air pollutants with hazardous effects to human health. The common usage of organic solvents in production industry is to clean lubricants, oils, waxes, paints, etc. These extremely hazardous pollutants might cause several important diseases such as Alzheimer's disease, leukoen-cephalopathy, multiple sclerosis (MS), and neurobehavioral disorders.

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