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Título: Reducción de costes de los recubrimientos sol-gel
Título original: Costing sol-gel coatings
Autor: Rupal Mehta
Resumen: A dry ice CO2 blasting pre-treatment technique and a novel curing method are set to reduce the costs of sol-gel coatings, according to inventors at VTT Technical Research Centre in Finland. They also claim that their technologies offer a more environmentally friendly approach.

Abrasive blasting with solid CO2, unlike wet pre-treatment techniques for substrate surfaces, does not rely on chemicals. This eliminates the numerous process steps and waste water and chemicals that result from traditional washing, rinsing and pickling of the material, while still producing a clean surface for coating adhesion. The method is also said to produce less waste than abrasive sandblasting.

With support from Finnish metal processing firms, the technique has been trialled on roll-to-roll coating of sheet metal strips.

The curing approach, meanwhile, exploits the substrate’s residual heat. ‘The method is applicable for products coming from some hot process, like hot-dip galvanising,’ says researcher Amar Mahiout at VTT. ‘They are clean [and] don’t need pre-treatment. [They] can be coated and the thermal energy accumulated in [the materials] does the curing without needing a oven. It is faster and cost effective.’

While the cost savings and trial results are commercially sensitive, Mahiout says they have demonstrated feasibility by curing coatings on hot-dip galvanised parts and those that are thermally sprayed, with seemingly no impact on coating functionality.

Professor Robert Akid, a specialist in anti-corrosion sol-gel coatings at Sheffield Hallam University, UK, is, however, cautious about the work’s potential until more technical information is revealed. He says, ‘The claims are rather bold. The success or not of replacing chemicals with CO2 as a pre-treatment route can only be assessed in terms of product lifetime performance and overall carbon footprint.
‘Solid CO2 sublimes forming CO2 gas, which is presumably discharged. Can this be reclaimed and recycled, and what are the costs of doing so? These are important questions to be addressed before the process is taken up by industry.’

Mahiout says, at present, the CO2 is not collected, although ‘it can be arranged’. He claims, ‘The CO2 used is a by-product of other industrial processes and thus it is produced and released anyway. The only CO2 surplus is because of the energy needed for solidification of gaseous CO2’. He acknowledges, however, that improving the blasting process by adding abrasive particles also creates waste.

With regards to the curing process, Akid says using residual heat for curing is ‘feasible’, but stresses the challenge to ‘match the curing requirements with the residual heat, particularly as there are adhesion issues when the thermal coefficients of the substrate and coating are significantly different’.

Mahiout agrees. He says, ‘The temperature [of the substrate] must be appropriate. If it is too high, you wait until it is cooled. If it is too low, this method is not applicable and conventional curing methods are needed’.

Akid adds, ‘It is not clear if the researchers see this approach as offering a stand-alone sol-gel coating. I have yet to see a sol-gel coating used without an additional top-coat. If a top-coat is to be applied, the cure conditions are crucial as they play a major role in adhesion and performance’.
Idioma: Inglés     País: UK     Año: 2010
Tipo: Artículo
Área: Procesos > Tratamientos superficiales y térmicos
Subsectores de aplicación: · Automoción e industria auxiliar
· Tratamientos superficiales y térmicos
Entidad: IOM3
Fuente: Materials World Magazine
Localización en fuente: 1 Apr
Descriptores: sol-gel coatings, pre-treatment, substrate surfaces
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