Research Progress And Performance Of Silane Films On Aluminium Alloys

The progress and corrosion resistance of silane films were studied. Theprogress parameters（hydrolysis temperature, concentration of silane, ratio of theethanol to water, pH value, hydrolysis time, dipping time, curing temperature,curing time） and rare earth Ce were discussed for their influence of the corrosionresistance and self-healing of silane films. Simultaneously, the corrosion resistance,electrochemical property, surface morphology and composition of silane films andsilane/rare-earth composite films were tested. The optimum progress of silane filmsand basic formula of silane solution were confirmed by orthogonal experiment;then on the basis of this, combined with the traditional processing method of rareearth transformation-process（P5:CeCl₃180mmol/L,H₂O₂（30%）13%,NaOH8mmol/L）,the silane/rare-earth composite films were prepared. The effect of part of theprocess paramenters on the corrosion resistance and compactability of thesilane/rare-earth composite films were studied by dropping corrosion test, saltspray test, solution immersion test and surface morphology. At the same time, thecorrosion resistance of silane films and silane/rare-earth composite films werecompared with the chromate conversion coating to explore the possibility ofreplacing the chromate conversion coating. The results show that when thehydrolysis temperature was30℃, the concentration of silane was3ml, the ratio ofthe ethanol to water was5/95, the pH value of the silane solution was13, thehydrolysis time was8h, the dipping time was10min, the curing temperature was120℃and the curing time was30min, the silane films were uniform and compact,which can effectively block corrosive ions into the matrix, and the Cu²⁺and H⁺corrosion resistance of silane films are better than the chromate conversion coating.However, the self-healing of silane films was bad, and the lasting corrosionresistance were worse than the chromate conversion coating. In order to solve theseproblems, when the rare-earth conversion time was5min, the curing temperaturewas100℃, the silane films were modified with the rare earth Ce to prepare thesilane/rare-earth composite films. Results shows that the preparativesilane/rare-earth composite films were tiny lumps, and the similar self-healing ofthe chromate conversion coating was shown. The lasting corrosion resistance wereincreased obviously, and the protective effect was more superior than the chromate conversion coating.