A Study on the Laser Removal of Epoxy Coatings on SS400 Surface by Beam Scanning Patterns

Shipyards are very interested in improving their working environment and resolving environmental pollution issues by replacing mechanical cleaning technologies used before and after painting processes with laser cleaning technology. Because epoxy paint is thickly coated, with a thickness of 200 μm or greater, it is difficult to remove using both laser cleaning and mechanical cleaning technologies. Therefore, this study tried to obtain effective cleaning results by controlling the process parameters when removing the thick epoxy coating using a Q-switching fiber laser cleaning system with an average power of 100 W developed by our research team. The pulse duration time of the laser is 150 ns. Additionally, in order to determine whether the cleaning was sufficient, the difference in laser-induced plume/plasma was compared. By controlling the beam scanning patterns, line overlap rate, and pulse overlap rate, it was possible to obtain effective cleaning results without introducing removal deviation. In addition, the NOP increased when the laser beam overlap rate increased. This increased the amount of heat input to the material and reduced the number of scans required to remove the epoxy paint. As a result of the plume/plasma analysis, less plume/plasma was generated as the paint was removed if the epoxy paint remained on the surface. On the other hand, when all of the paint was removed, a higher brightness of plume/plasma generated by evaporation of the bare metal was observed.

Effects of Mangrove Plant Extraction on Adhesion Strength in Coating of Epoxy

Steel is an alloy of ferrous metal with a maximum carbon content of 2%. This material is widely used for jetty building structures at rivers, estuary, and coastal areas. Corrosion of steel can occur due to several factors, such as the steel material itself and the surrounding environmental factors. One of the corrosion is biocorrosion that occurs due to the presence of biofouling. This study aims to determine the effect of adding extraction of mangrove (Avicennia marina) as an antifouling compound mixed in epoxy paint through adhesion strength parameter. Then the alloy was applied as a coating on the ASTM A36 steel specimen. The variation of coating composition were 100% of epoxy paint, 90%:10% (epoxy paint and extraction of Avicennia marina), 80% : 20% and 70% : 30%. The results showed that the adhesion strength occurred in 100% of epoxy paint (10.15 ± 0.64 Mpa). The adhesion strength was 8.86 ± 0.21 Mpa, 8.50 ± 0.03 Mpa, and 8.19 ± 0.07 Mpa at ratio of composition coating 90%: 10%, 80%: 20%, and 70%: 30%, respectively. In conclusion, the more mangrove extraction was added, the smaller the adhesion strength.

Polyaniline as Additive to Improve the Anticorrosive Properties of Commercial Paint

Corrosion is one of the great problems that many industries face and that generates losses of millions of dollars worldwide. The aim of this work was to evaluate the capacity of polyaniline to increase the anticorrosive capacity of a commercial epoxy paint. Polyaniline was chemically synthesized by oxidation with ammonium persulfate and doped with oleic acid. Polyaniline was added to the paint in various concentrations to evaluate its behavior as an additive to improve the anticorrosion capacity on stainless steel samples. An electrochemical characterization by polarization curves and visual observation was carried out to evaluate the anticorrosive behavior of the modified paints. The results showed that the corrosion rate determined from the tafel plot was lower in the steel samples covered with paint and polyaniline. The concentration of 0.8% of polyaniline in the paint showed a corrosion rate 12 times lower than that of the polyaniline-free paint. Additionally, visual observations and measurements of failed area carried out by applying an accelerated corrosion process by immersion in a 3.5% NaCl aqueous solution, allowed determining that, at a time of exposure of 300 h, corrosion inhibition can be achieved 26 times greater with the addition of 0.8% polyaniline. These results allowed to conclude that the addition of polyaniline by means of a simple mixture, significantly improved the anticorrosive protection capacity of a commercial epoxy paint.

The effect of TiO2 Nanoparticles in Epoxy Paint Formulation on Metal Surfaces

Currently, epoxy paint is being widely used in the industry. Nanotechnology can create many small nanometer-sized materials with many applications, it has brought many outstanding properties to epoxy paints. The aim of this study is to investigate the effect of TiO2 nanoparticles in epoxy paint formulation towards metal surface. We created a sample of two-component epoxy paint, part A is epoxy resin, anti-sedimentation, dispersant substance, foam breaking agent, cover substance, solvent, other additives, and part B is a curing agent for epoxy resins. Methods of analyzing the properties of the epoxy paint film are based on Vietnam standards. TiO2 nanoparticles are a good coating substance in epoxy paint. The study results showed that TiO2 nanoparticles have increased the properties of the epoxy paint film, improving the Impact and Glossy of the epoxy paint film. TiO2 nanoparticles increases from 1% to 6% by weight, the impact increased by about 18.75%. (80 to 96 kg.cm), Glossy 600 increased by about 12.79% (80 to 97). Adding TiO2 nanoparticles to epoxy paint has increased Impact and Glossy for the paint film. The higher the rate of TiO2 nanoparticles, the better the properties of the epoxy paint film. Therefore, TiO2 nanoparticles are a good coating in epoxy paint, it improves the properties of the paint film. Because the cost of nanomaterials is higher than that of normal coating materials, the nanomaterial should only be added with a ratio of about 2-5% by weight.

USE OF MODIFIERS FOR INCREASE OF OPERATIONAL PROPERTIES OF PAINT COATINGS ON THE BASIS OF THE EPOXY FILM-FORMING (review)

Epoxy oligomers are one of the most widespread synthetic polymers who during already enough long time apply to manufacturing of paint and varnish materials. Possessing number of valuable properties, epoxy paint and varnish materials have also shortcomings for which elimination use different receptions, including physical and chemical updatings using different mono- and elastomeric, silicon- and organophosphorous and other connections. The main attention is given to use of different modifiers for improvement of operational properties of anticorrosion paint coatings.

Effect of Surface Modification and Fibre Content on the Mechanical Properties of Coconut Fibre Reinforced Concrete

In the past few decades, concrete has been the most widely used material for structural applications in the world and uses steel reinforcement as aide to meet the flexural, tensile and ductility demands required of concrete structures. Manufacturing of concrete and steel reinforced concrete structures is associated with millions of tons of carbon dioxide emissions and mineral waste. This activity is also responsible for the depletion of a large number of non-renewable resources. Reinforcing steel is also a high cost material, consumes a lot of energy in its production. Consequently, the use of natural fibres as an alternative for steel reinforcement is widely investigated, to promote the use of sustainable concrete structures. This study aims to investigate the effect on durability, flexural, compressive, tensile properties and workability of concrete by incorporating coir fibre at varying fibre content to find the fibre content which gives optimum results. The fibre contents used were 0%, 0.5%, 1.0%, 1.5% and 2.0% by weight of cement. Furthermore, the effect of modifying the surface of the coir fibres by alkali treatment (i.e. 5 wt.% NaOH solution) and coating the fibres with epoxy paint and polyurethane varnish on coir fibre reinforced concrete (CFRC) were also investigated. Tests conducted on the CFRC specimens included slump test and flexural, compressive and tensile strength tests. Water absorption and sorptivity tests were also conducted to investigate the durability. Slump (workability) and unit weight reduced with an increase in fibre content. The surface modification methods used, had resulted in an increased workability and a reduced unit-weight. A coconut fibre content of 1% produced the best combination of flexural, tensile and compressive properties. Water absorption and sorption rate per unit time, increased with an increase of coir fibre content. It is also found that epoxy paint and alkali treatment of the fibres has a positive effect on the mechanical strength properties and also the durability and workability of the CFRC specimens. However, polyurethane varnish coating had a detrimental effect on the mechanical strength properties of the CFRC specimens.