European project looks for greener surface treatments

AMAugust16News - Titania
AMAugust16News - Titania

SEALANT project arises as a new contribution towards the challenge of avoiding the use of toxic and potentially harmful materials in design, production and maintenance of aircraft.

Chromic acid anodising (CAA) has been extensively used during decades in aircraft manufacturing thanks to its excellent performance. Chromate is a corrosion preventative for aluminium, and works extremely well as a soluble inhibitor in cooling water systems, inhibiting pigment in paints and as a component in deoxidiser, conversion coatings and anodised coatings.

However, hexavalent chromium is known to be carcinogenic and to cause a wide array of medical problems, including cancer. Consequently, it has been included in the list of substances of several regulation banning or restricting its use such as REACH (European Union regulation concerning the Registration, Evaluation, Authorisation & restriction of Chemicals).

Specifically, this European initiative focuses on optimising a Chromium-free sealing process for thin layer sulfuric acid anodising (SAA) and evaluate its industrial viability as eco-friendly alternative to CAA for aluminium unpainted parts.

And Titania, the company of the Andalusian cluster specialised in aeronautical materials and processes, is coordinating this project along with institutions such as the University of Cadiz (UCA), the Technology Centre of Miranda de Ebro (CTME), the Technology Centre Cidetec and the company Innomat Coatings. This is the first European project in which Titania participates, and also the first in which assumes the role of coordinator.

On 6th July 2016, at Titania’s facilities, the kick off meeting of SEALANT project was held, belonging to the 2nd Call for Proposals (CFP02) of the Clean Sky 2 Joint Undertaking. Titania will coordinate the activities carried out by the rest of the consortia, but also has technological responsibilities within the project: the search of a non-commercial sealing solution for SAA process; to optimise at laboratory scale the formulation of AA2024 alloys; to study the optimised conditions on other aluminium alloys of interest; evaluation at pre-industrial scale (with baths of 125L) and standard characterisation tests.

The University of Cadiz will also provide support for the technical coordination of the project, and among other functions, it will study and analyse results through the employment of Analysis of Variance (ANOVA) statistical models; it will conduct the advanced characterisation of processed samples; it will investigate on protection mechanisms and determine the boundary conditions of the process.

Regarding the corrosion behaviour, UCA will also implement the Design of Experiment (DoE) techniques to plan a comprehensive approach to the experimental process conditions, a new system that streamlines the research activity by planning tests, instead of more traditional system of trial and error.

The project, which lasts two years, has the following technological objectives:

  • To improve the corrosion behaviour of AA2024 subjected to the anodising and sealing processes previously developed, under surface treatment free of chromium.

  • For this purpose, the sealing parameters of two different solutions, type and concentration of chemicals, pH, temperature, time, conditions used for rinsing and drying.

  • To define an optimum experimental condition for the sealing processes at laboratory scale. The selection of optimal parameters will be based on corrosion resistance, through salt spray standardised test.

  • To implement the process to other aluminum alloys of interest for the project.

  • To implement the optimised sealing processes in pre-industrial scale. A surface treatment line with baths of 125L will be employed. The corrosion behaviour of the samples and stability of the solutions will be compared with previous data obtained at lab-scale.

  • To implement the sealing process in an industrial scale on demonstrators.

Another important objective for this project is to evaluate the economic cost and the environmental impact of the new process of sealing. For this purpose two views will be considered: the environmental and toxicity classification of chemicals compounds during formulation phase will be served as useful information for Ecodesign process, and Life Cycle Assessment (LCA) of the two sealing solutions from formulation to end of life scenario.



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