SEALANT

The project:

Chromic acid anodizing (CAA) has been extensively used during decades in aircraft manufacturing thanks to its excellent performance. In general terms, Chromate is an outstanding corrosion preventative for aluminium. It 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 regulations banning or restricting its use such as REACH (European Union regulation concerning the Registration, Evaluation, Authorisation & restriction of Chemicals).

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. Specifically, this European initiative focuses on optimizing a Chromium-free sealing process for thin layer Sulfuric Acid Anodizing (SAA) and evaluate its industrial viability as eco-friendly alternative to Chromic Acid Anodizing (CAA) for aluminium unpainted parts.

The project 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.

– 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 standardized test.

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

– To implement the optimized 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 are 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.

Partnership:

The consortium of the SEALANT project comprises 5 organisations,all from Spain. Titania, a company of the Andalusian cluster specialized in aeronautical materials and processes coordinated this innovative project along with institutions such as the University of Cadiz (UCA), the Technology Center of Miranda de Ebro (CTME), the company INNOMAT COATINGS and CIDETEC.

Our role:

The role of CIDETEC is to support in the optimization of the conditions to carry out the industrial scaling-up of the processes and to control the anodizing industrial baths. CIDETEC also test and validatethe demonstrators manufactured in INNOMAT.