Deposição Eletroassistida De Ortossilicato De Tetraetila (Teos) Como Pré-Tratamento Para a Pintura De Alumínio Aa1100

Abstract

ResumoA técnica convencional de produção de filmes de organossilanos por imersão pode promover a formação de pré-tratamentos pouco homogêneos, prejudicando a sua proteção por barreira contra a corrosão e a aderência de tintas. Sendo assim, a técnica de deposição eletroassistida, baseada na promoção da eletrólise da água e consequente favorecimento das reações de condensação do organossilano, é estudada com o objetivo de promover a formação de filmes com menos descontinuidades. Neste trabalho a deposição eletroassistida foi comparada com a técnica convencional de imersão, bem como com a cromatização hexavalente. O precursor utilizado neste trabalho foi o ortossilicato de tetraetila (TEOS), um silano não funcionalizado. A comparação entre os pré-tratamentos foi realizada através de ensaios de corrosão acelerada em névoa salina, medida de aderência de tinta, espectroscopia de impedância eletroquímica e espectroscopia de energia dispersiva. Os resultados indicam que a deposição eletroassistida em potenciais catódicos promoveu maior cobertura do substrato. Palavras-chave: Silano; Deposição eletroassistida; Pré-tratamento; Alumínio. TETRAETHYL ORTHOSILICATE (TEOS) ELECTRO-ASSISTED DEPOSITION AS A PRETREATMENT FOR PAINTING AA1100 ALUMINUM ALLOY AbstractThe standard method for the production of organosilane films by dip-coating may lead to non-homogeneous pretreatment layers, weakening its barrier protection against corrosion and paint adhesion. Therefore, the electro-assisted deposition technique, based on promoting water electrolysis and the consequent favoring of condensation reactions of the organosilane, is studied with the aim of promoting the formation of less discontinuous coatings. In this work the electro-assisted deposition was compared to the standard dip-coating method and to hexavalent chromate conversion coating. The precursor used in this work was tetraethyl orthosilicate (TEOS), a non-functional silane. The comparison between the pretreatments was carried out by salt spray tests, paint adhesion measurement, electrochemical impedance spectroscopy and energy dispersive spectroscopy. The results indicate that the electro-assisted deposition in cathodic potentials promoted higher coverage of the substrate.

Influence of Concentration and pH of Hexafluorozirconic Acid on Corrosion Resistance of Anodized AA7075-T6

“…Fig. 8 -a shows a simple scheme of the unsealed porous film and indicates the components of its electrical impedance, which is in accordance with some other schemes in literature 10,16,[19][20] . Table 4 shows the values of electrical components, as well as the value of chi-square (x²).…”

“…Hence, a simple sanding procedure was performed, with #320 and #600 SiC papers, which promoted an intermediate roughness on the surfaces. This step was followed by degreasing with the commercial product Saloclean 667N (Klintex) at 70ºC for 10 min 20 , and later rinsing with deionized water and drying with hot air. The next steps of preparation were chosen based in previous works with different aluminum alloys before anodizing [21][22][23] .…”

“…When the sealing process is effective, 2 time constants can be clearly distinguished on the EIS diagrams. One of the constants can be associated with the barrier layer, in low frequencies, and the other with the sealed porous layer, in middle to high frequencies 16,20 . This behavior was expected for samples sealed with boiling water, once its morphological characterization indicated a well-sealed surface, i.e., hydrated alumina plugging the pore openings (Figure 2 -c).…”

Green Nanocoatings Based on the Deposition of Zirconium Oxide: The Role of the Substrate

“…The potentials used in this work were −1.0 V OCP and −1.5 V OCP , generating the samples named “EAD −1.0 V” and “EAD −1.5 V”, respectively. Such potentials were chosen on the basis of our previous experience [ 20 , 21 ]. Samples coated by both dip-coating and EAD were further post-treated for 2 h at 100 °C, as aging step treatment to achieve the dehydration of the oxide layer and the reduction of defects [ 22 ].…”