Comparative investigation of the adhesion of Ce conversion layers and silane layers to a AA 2024-T3 substrate through mechanical and electrochemical tests

Abstract

Cerium conversion layers and silane films are among the potential substitutes for the carcinogenic chromate conversion layers used to protect high-strength Al alloys. In the present work the adhesion of a cerium conversion layer and of a silane film to an aluminium alloy (AA) 2024-T3 substrate was investigated using mechanical and electrochemical tests. Scanning electron microscopy (SEM)-X ray energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FT-IR) and X ray photoelectron spectroscopy (XPS) were used to characterize the layers prior and after the mechanical test consisting of ultrasonic rinse in deionized water during 30 minutes. Mechanically tested and untested layers were also submitted to electrochemical impedance spectroscopy (EIS) and anodic polarization measurements in 0.1 M NaCl solution. The results of the characterization tests have pointed to a stronger adhesion of the Ce layer to the substrate in comparison with the silane film, which was confirmed by the electrochemical tests. The adhesion between the silane film and the Ce conversion layer was also tested, to evaluate the possibility of using the system as a protective bi-layer in accordance with the new trends being developed to substitute chromate conversion layers.

Enhancement of the Corrosion Protection Properties of a Hybrid Sol-Gel Based Silane Film through Impregnation of Functionalized Graphene Oxide Nanosheets

“…Chemical and surface characterization of various silane coatings on steel surface.-FT-IR spectrum of pure silane coating (SC coating) and silane coating with 0.2 g/L GO (SC-GO coating), AGO (SC-AGO coating) and IGO (SC-IGO coating) nanosheets are presented in Figure 4. In the case of SC coating, the characteristic bands are O-H stretching of Si-OH and H 2 O at 3436 cm −1 , 50 C-H stretching of -CH 3 groups at 2980 and 2917 cm −1 , 51 C=O stretching vibration of acetic acid at 1718 cm −1 , 52 O-H deformation of water molecules at 1633 cm −1 , 47 Si-C vibration of Si-CH 3 at 1274 cm −1 , 51 Si-O-C and Si-O-Si antisymmetric vibration at 1140 and 1050 cm −1 , 23 respectively, OH stretching vibration of Si-OH at 906 cm −123 and Si-O-Si symmetrical stretching at 776 cm −1 . 51 In the spectrum of SC-GO coating, all characteristic bands related to the SC coating appeared, while the peak at 1633 cm −1 is attributed to the C = C skeletal vibrations of the GO aromatic ring and deformation of the O-H band of water molecules trapped in the coating structure.…”

Estudo das condições de obtenção do filme viniltrietoxisilano na proteção contra a corrosão do aço galvanizado

“…O formato dos diagramas de Nyquist para as amostras revestidas se difere da amostra sem revestimento da amostra de aço galvanizado sem filme de silano (aço galvanizado), pois na amostra sem revestimento de silano é observada a formação de dois arcos capacitivos, enquanto que nas amostras revestidas com silano é observado apenas um. Pela análise dos diagramas -ângulo de fase x log f -fica claro que a amostra de aço galvanizado possui duas constantes de tempo bem definidas, sendo uma na região de altas frequências devido a interação eletrólito/camada de Zn e uma outra na região debaixas de baixas frequências, resultante da interface Zn/Fe [33,34,35].…”

“…No diagrama de ângulo de fase x log f (Figura 4C) nota-se uma deformação de média para baixas frequências, que também é observada no diagrama de log |Z| x log f (Figura 4B), devido às reações interfaciais galvanizado/substrato. A constante de tempo relativa ao filme de VS está deslocada para altas frequências indicando à resistência a resistência às reações interfaciais filme/eletrólito [35,36,37,38].…”

Integration of Anhydrous Sodium Acetate (ASAc) into Concrete Pavement for Protection against Harmful Impact of Deicing Salt

“…59 In addition, the presence of sodium hydroxide (NaOH) in the 60,61 Another reason for the increase in C-H bonds is believed to be the replacement of -OH groups by -CH 3 groups, which in turn bond with silicon atoms in the cement, resulting in the formation of a hydrophobic component integrated within the mix (organosilicon bonds). [62][63][64][65][66][67] This could result in improving the hydrophobicity of the concrete treated with ASAc ( Supplementary Fig. S4).…”