Isabel Rute Filipe Cerveira Nunes Fontinha
@lnec.pt
Departamento de Materiais
Laboratório Nacional de Engenharia Civil
EDUCATION
PhD (Materials and Ceramic Engineering)
RESEARCH INTERESTS
Durability of metallic materials used in construction and respective metallic and inorganic coatings in natural environments.
Corrosion and conservation of metallic cultural and architectural heritage.
Sol-gel coatings for corrosion protection.
Scopus Publications
Scholar Citations
Scholar h-index
Scholar i10-index
Scopus Publications
Isabel Fontinha and Elsa Eustáquio
MDPI AG
Anodizing is commonly used for corrosion protection of aluminum and its alloys in the construction industry. The anodic aluminum oxide (AAO) coating has a high ability to prevent the development of extensive pitting corrosion in aluminum substrates, particularly in marine sites, as was observed during a 10-year atmospheric corrosion study carried out in several marine and industrial sites. However, this study also evidenced that this coating can be highly affected by the deposition of particulate material in industrial polluted environments, sometimes in unexpected ways. This study presents information on the atmospheric corrosion of anodized aluminum exposed at two different chemical industrial complexes: a fertilizer production plant and a pulp and paper mill. Visual assessment of surface changes, pitting depth and mass variation with exposure were determined to quantify the degradation suffered. Additionally, SEM/EDS analyses were carried out on the exposed surfaces. Based on the results obtained, the role played by the deposition of airborne particles present in the two environments with respect to the type and level of damage observed is discussed. Deposits of roasted pyrite ash and phosphates or of wood chips and lime particles enhanced pitting corrosion or caused dissolution of the AAO coating.
Rita Figueira, Isabel Fontinha, Carlos Silva, and Elsa Pereira
MDPI AG
Corrosion degradation of materials and metallic structures is one of the major issues that give rise to depreciation of assets, causing great financial outlays in their recovery and or prevention. Therefore, the development of active corrosion protection systems for metallic substrates is an issue of prime importance. The promising properties and wide application range of hybrid sol-gel-derived polymers have attracted significant attention over recent decades. The combination of organic polymers and inorganic materials in a single phase provides exceptional possibilities to tailor electrical, optical, anticorrosive, and mechanical properties for diverse applications. This unlimited design concept has led to the development of hybrid coatings for several applications, such as transparent plastics, glasses, and metals to prevent these substrates from permeation, mechanical abrasion, and corrosion, or even for decorative functions. Nevertheless, the development of new hybrid products requires a basic understanding of the fundamental chemistry, as well as of the parameters that influence the processing techniques, which will briefly be discussed. Additionally, this review will also summarize and discuss the most promising sol-gel coatings for corrosion protection of steel, aluminium, and their alloys conducted at an academic level.
I R Fontinha, M M Salta, M L Zheludkevich, and M G S Ferreira
Portuguese Society of Electrochemistry
The organic-inorganic hybrid sol-gel films, the structure of which comprises interconnected inorganic and organic networks have been reported as an environmentally friendly anti-corrosion pre-treatment for several metals, including aluminium alloys. In this paper, an epoxy-silica-zirconia hybrid sol-gel coating was synthesized from glycidoxypropyltrimethoxysilane (GPTMS) and zirconium npropoxide (TPOZ) precursors and applied to EN AW-6063 alloy by dip-coating. To promote the organic network formation through the epoxy group polymerization at room temperature, two types of amine crosslinkers were added during synthesis: diethylenetriamine (DETA), in different concentrations, and a tri-functional aminosilane. The evolution of the curing process and the corrosion behaviour of the coated aluminium alloy specimens were evaluated by Electrochemical Impedance Spectroscopy (EIS) in 0.5 M NaCl. The morphology and surface chemistry of the hybrid coatings were characterized by Energy Dispersive Spectroscopy (EDS) coupled with Scanning Electron Microscopy (SEM) and by Fourier Transform Infrared Spectroscopy (FTIR). The results obtained revealed that the sol-gel coatings with lower amine ratios required longer curing times, but showed the best anticorrosive performance with time. The increase in amine concentration has led to a more cross linked organic network, resulting in higher initial coatings resistance; however it has turned coatings more hydrophilic, prone to rapid degradation in water.
I Rute Fontinha, Maria Manuela Salta, Mikhail L. Zheludkevich, Mário G. S. Ferreira, Rita Bacelar Figueira, Elsa Vaz Pereira, and Carlos J. R. Silva
The Electrochemical Society
Aluminium alloys of 6000 series can suffer severe corrosion in polluted (acidic) and/or marine environments and in contact with alkaline media like fresh cementitious materials. Therefore, architectural aluminium components are often coated, what requires its surface pre-treatment. Organic-inorganic hybrid (OIH) sol-gel coatings have been proposed as an effective, environmental compliant new pre-treatment for aluminium coating. In this work, an epoxy-silica-zirconia sol-gel coating was synthesized and applied on EN AW-6063 alloy. Cerium nitrate was incorporated as corrosion inhibitor. Cerium doped and undoped OIH coatings were exposed to neutral, acidic (pH~3) and alkaline (pH~10) chloride solutions. Electrochemical impedance spectroscopy (EIS) and SEM/EDS characterization of coated samples revealed that the best performance is achieved in the neutral and the worst in the acidic solution. In the alkaline solution, the cerium doped coatings exhibited much better anticorrosive performance than the undoped ones, clearly evidencing the beneficial role of the corrosion inhibitor in this media.
Rute I. Fontinha, Manuela M. Salta, Mikhail L. Zheludkevich, and Mário G.S. Ferreira
Trans Tech Publications, Ltd.
The organic-inorganic hybrid sol-gel films have been reported as an effective anti-corrosion and environmentally friendly alternative to Cr(VI) pre-treatment for aluminium alloys. The sol-gel process used to obtain these coatings allows the variation of the different synthesis parameters to achieve coatings with optimized properties. In this work, hybrid films with different Zr/Si ratios were synthesized from glycidoxypropyltrimethoxysilane (GPTMS) and zirconium n-propoxide (TPOZ) precursors. Electrochemical Impedance Spectroscopy (EIS) was used to evaluate the corrosion behaviour of coated aluminium specimens in 0.5 M NaCl solution. The morphology and chemical structure of the hybrid coatings prepared were studied by Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS), Fourier Transformed Infrared Spectroscopy (FTIR) and Thermo Gravimetric Analysis (TGA). It was found that increasing Zr/Si ratio leads to a more cross linked inorganic network, resulting in higher initial coatings resistance, but may turn coatings more hydrophilic, prone to rapid degradation in water, due to a less connected organic network. Consequently, the best anticorrosive performance derives from the balance between the two opposite trends and it was achieved with Zr/Si molar ratio of 0.25.