A review of blasting waste generation and management in the ship repair industry.

Solid blasting waste generated from coating removal during ship repair and maintenance poses environmental challenges. This paper presents a review of the generation, characterization, and treatment of blasting waste in the ship repair industry. The quantities, properties, and environmental impacts of the generated blasting waste are summarized and analyzed, and the results indicate that blasting waste has a high generation rate and/or high toxicity. As alternatives to landfill, available blasting waste treatment methods include hydrometallurgical leaching, physical/physicochemical separation, thermal treatment, and direct utilization in the production of building materials. The advantages and disadvantages of these treatments are reviewed and compared. The production of building materials from blasting waste is currently attractive owning to its economic benefits and technical simplicity, whereas recycling blasting waste for high-value applications is gradually gaining research interest. The high dependence of the choice and performance of treatment methods on the waste type and characteristics is highlighted. The results emphasize the interest in conducting more research on physiochemical and thermal properties and the environmental effects of blasting waste. This review suggests that future research should focus more on paint waste management because of the restricted application of dry abrasive blasting and the development of nonabrasive blasting methods in the ship repair industry.

Characterization and Release Mechanisms of Aerogel-Encapsulated Biocide Crystals for Low-Loading and High-Utilization Antifouling Coatings.

Silica aerogel-encapsulated biocide crystals can potentially enhance the protection efficiency of antifouling coatings, thereby lowering the impact on nontarget aquatic life. In the present study, copper pyrithione (CuPT) crystals are encapsulated by silica aerogel to obtain loadings of 50-80 wt % CuPT. For optimal design of the heterogeneous particles and mapping of the underlying biocide release mechanisms, the aerogel-encapsulated biocide crystals are characterized by scanning (transmission) electron microscopy, energy-dispersive X-ray spectroscopy, thermal gravimetric analysis, mercury intrusion porosity, Brunauer-Emmett-Teller analysis, and light scattering. The microscopic examination demonstrates that the elongated CuPT crystals are encapsulated by a thin highly porous silica layer. When varying the CuPT loading of the aerogels, it is possible to tune the particle size, pore volume, and specific surface area of the aerogels. Furthermore, this study suggests that the hydrophilic aerogel-encapsulated CuPT, when used in antifouling coatings, attracts seawater and contributes to an efficient controlled release of active CuPT.

Adhesion between coating layers based on epoxy and silicone.

The adhesion between a silicon tie-coat and epoxy primers, used in marine coating systems, has been studied in this work. Six epoxy coatings (with varying chain lengths of the epoxy resins), some of which have shown problems with adhesion to the tie-coat during service life, have been considered. The experimental investigation includes measurements of the surface tension of the tie-coat and the critical surface tensions of the epoxies, topographic investigation of the surfaces of cured epoxy coatings via atomic force microscopy (AFM), and pull-off tests for investigating the strength of adhesion to the silicon/epoxy systems. Calculations for determining the roughness factor of the six epoxy coatings (based on the AFM topographies) and the theoretical work of adhesion have been carried out. The coating surfaces are also characterized based on the van Oss-Good theory. Previous studies on the modulus of elasticity of the polymers involved have also been considered. It was found that adhesion problems might be due to inadequate wetting, the significantly different topographies, and differences in the mechanical strengths of the epoxies. Acid-base interactions calculated from the van Oss-Good theory were found useful in explaining the enhanced adhesion for some epoxy/silicon surfaces.

Presence and effects of marine microbial biofilms on biocide-based antifouling paints.

Marine microorganisms are capable of successfully colonizing toxic surfaces through the formation of biofilm structures. In this article, most of the literature reporting the presence of marine biofilms on chemically-active antifouling paints is briefly reviewed. Of special concern is the influence of the dense extracellular polymeric substances (EPS) matrix on the release rate of the compounds involved in antifouling paint performance (i.e. active compounds and controlled-release binder molecules). A deeper understanding of these phenomena is of interest for both environmental legislators and paint formulators.

Estimation of polishing and leaching behaviour of antifouling paints using mathematical modelling: a literature review.

The development of chemically active antifouling paints has traditionally been based on an empirical approach. Optimisation and evaluation of novel and existing products are frequently conducted by means of, for example, systematic paint rotary tests in the laboratory or at sea sites. In this review, the usefulness of combining rotary experiments with the development of detailed mathematical models of paint behaviour will be discussed with reference to the relevant literature. Mathematical models can generally be used in the design of suitable release systems for various active components such as proteins or biocides, as well as for the estimation of release rates from different compositions of paints under various seawater conditions. Insoluble matrix, soluble matrix and self-polishing paints will be considered. Simulations from recent publications that show the effects of dynamic changes in seawater on paint behaviour will be presented. Examples of potential uses of paint models for accelerated polishing and leaching tests and screening of novel paint components will also be discussed. Directions of future modelling work are suggested.

Experimental study of drag resistance using a laboratory scale rotary set-up.

This work covers an experimental study of the drag resistance of different painted surfaces and simulated large-scale irregularities, viz. dry spraying, weld seams, barnacle fouling and paint remains. A laboratory scale rotary set-up was used to determine the drag resistance, and the surface roughness of the samples was determined by means of two different stylus-based methods, one having a 1.6 mm ball stylus (giving the macro-roughness) and the other having a needle type stylus (giving the micro-roughness). It is demonstrated that, in the case of ideal painted surfaces (low macro-roughness), the micro-roughness is much more important than the macro-roughness. On the other hand, the study also indicates that larger scale irregularities have a much greater influence on the drag resistance compared to measurements of the paint system alone.