Danqing Zhu

Corrosion protection of AA 2024-T3 by bis-[3-(triethoxysilyl)propyl]tetrasulfide in sodium chloride solution. Part 2: mechanism for corrosion protection

Abstract The corrosion protection of AA 2024-T3 by films of bis-[3-(triethoxysilyl)propyl]tetrasulfide (bis-sulfur silane) was studied in a neutral 0.6 M NaCl solution using potential transient, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. The results showed that a highly crosslinked or dense interfacial layer that developed between the silane film and the aluminum oxide is the major contribution to the corrosion protection of AA 2024-T3. The formation of this interfacial layer heavily restricts pit growth underneath via retarding the transport of corrosion products, as well as effectively blocks a number of cathodic sites available for cathodic reactions.

Corrosion Protection Properties of Organofunctional Silanes—An Overview

The aim of this paper is to review the development and state of the art in the application of certain organosilicon compounds known as trialkoxysilanes (or simply silanes) to the problems of the metal finishing industry. The ultimate goal of this work is the replacement of chromate passivation and paint pretreatments, as well as overcoming the shortcomings of organic coatings formulated in the modern environmentally friendly world, thus without chromate or chromated pigments, volatile organic carbon (VOC) containing compounds or harazardous air pollutants (HAPs).

Electrochemical Impedance Spectroscopy of Bis-[Triethoxysilypropyl]Tetrasulfide on Al 2024-T3 Substrates

Abstract Thin films of the hydrolyzed silane bis-[triethoxysilylpropyl]-tetrasulfide (sulfane) were deposited on alkaline-cleaned Al 2024-T3 panels and investigated by electrochemical impedance spe...

Corrosion protection of AA 2024-T3 by bis-[3-(triethoxysilyl)propyl]tetrasulfide in neutral sodium chloride solution. Part 1: corrosion of AA 2024-T3

This study consists of two parts. In the first part, the corrosion of 2024-T3 aluminum alloy (AA 2024-T3) was studied using scanning electron microscopy and energy-dispersive X-ray spectroscopy. The results showed that the anodic S phase (Al2CuMg) particles dealloyed Al and Mg during the 3.5 h of immersion in a neutral 0.6 M sodium chloride (NaCl) solution; with the dealloying of Mg being the most severe. Simultaneously, a heavy dissolution was also observed for the surrounding Al matrix of the S phase particles. This Al dissolution is likely to be caused by a local alkalization resulting from the coupled cathodic reaction (water and/or oxygen reduction). Such corrosion in AA 2024-T3, however, can be inhibited efficiently after the treatment of bis-[3-(triethoxysilyl)propyl]tetrasulfide (bis-sulfur silane). The associated studies on bis-sulfur silane treated AA 2024-T3 will be presented in the second part.

Silane based chromate replacements for corrosion control, paint adhesion, and rubber bonding

Abstract An overview is given of the use of silanes for corrosion control of metals and bonding of silane treated metals to paint systems and rubber compounds. Examples are given of corrosion protection of cold rolled steel, galvanised steel, aluminium, and magnesium, both painted and unpainted. Emphasis in this work has been on the use of bis-silanes rather than the conventional mono-silanes. It is shown that mixtures of a bis-amino and a bis-polysulphur silane work with a wide range of metals and paint systems. A model is described which is largely based on electrochemical impedance spectroscopy (EIS) measurements.

Structural characterization of bis-[triethoxysilylpropyl]tetrasulfide and bis-[trimethoxysilylpropyl]amine silanes by Fourier-transform infrared spectroscopy and electrochemical impedance spectroscopy

Bis-[triethoxysilylpropyl]tetrasulfide (or bis-sulfur silane) and bis-[trimethoxysilylpropyl] amine (or bis-amino silane) were deposited on 2024-T3 aluminum alloy (AA 2024-T3). The structures of the films were characterized using Fourier-transform infrared spectroscopy (FTIR) and electrochemical impedance spectroscopy (EIS) techniques. The results showed that: (1) The silane structures were affected significantly by the hydrolysis time of the silane solutions. A minimum hydrolysis time is required to obtain a crosslinked silane film. (2) Hydrolysis progressed more readily and faster in the bis-amino silane system than in the bis-sulfur silane system, probably due to the catalytic action of the amine of the bis-amino silane. (3) Both silane systems experienced significant crosslinking upon curing at 100°C, during which denser interfacial layers were formed via crosslinking in the interfacial regions. The interfacial layer contributes to corrosion protection of metals by silanes. (4) A new phase was observed in the fully cured bis-amino silane film after aging in the atmosphere. This new phase is likely to be carbamates and bicarbonates formed via a reaction between the secondary amino groups, carbon dioxide, and moisture absorbed from the atmosphere.