Rare Earth Salt-doped Water-based Silane Films And Their Application In Anticorrosive Painting System

Coating systems have been widely applied to metal surface to provide a dense barrier against the corrosive species. A coating system consists of at least two individual compartments:the pretreated conversion layer (CL) and topcoat. Most of the effective corrosion protection systems for metals use chromate or phosphate films as the CLs, despiteof the fact that these conventional CLs offer satisfactory adhesion and ensure excellent corrosion protectionproperties of the final coating system, they are environmentally undesirable. Chromium (VI) is high toxic and has carcinogenic effects on humans, while phosphorus can lead to water eutrophication. Thus, strict environment regulations will ban the use of chromate and phosphate in corrosion protection systems. In the last few years great efforts have been made in order to find environmentally friendly substitutes,one of the prospective candidates is sol-gel silane thin films. Silane films applied on metallic substrates provides good adhesion between the metal and topcoat.Unfortunately, silane films produced withconventional technique aretoo thin to provide enough corrosion protection for substrates. The need of a high concentration of alcohol in silane solution poses a major obstacle in the introduction of these alcohol-based silanes into existing industrial systems. In this thesis, we report a pretreated layer based on water-basedsilane (GPTMS) solution doped with cerium nitrate, aiming to produce an environmentally friendly coating system applied on AA2024-T3and mild steel substrates. The main contents are listed as follows(1) Cerium nitrate doped water-based silane films wereprepared on AA2024-T3. The investigation was carried out by immersion the pretreated substrates in0.1M NaCl solution, the results shown that pretreatments based on doped silane solutions provide good protection of AA2024-T3substrates.The role of cerium nitrate was also investigated by using X-ray energy dispersive spectroscopy combined with in-situ infrared spectrometry and MALDI-TOF-MS.(2) The water-based silane film used as the pretreated layer of metal/epoxy coatings system has good adhesion both to the substrate and to the topcoat. The EIS response suggested that the corrosion protectionperformance of water-based silane, especially with topcoat, is comparable to that ofalcohol-based silane.The water-based silanefilm doped with cerium nitrate could further improve thepropertiesof corrosion resistance.