Process for cathode electrolytic deposition of rare-earth conversion film

Abstract

The present invention provides a method of forming non-toxic and anticorrosive RE conversion film on aluminum alloy part surface. The technological scheme is that during treating aluminum alloy part with treating solution comprising RE salt and oxidant, one DC power source is applied, so as to form homogeneous compact protecting RE film on the surface of aluminum alloy part. The present invention has the common effect of applied current and the treating solution, and possesses the advantages of simple apparatus, easy operation and low cost.

Description

technical field [0001] This patent relates to the electrolytic deposition process of the chemical conversion film of aluminum alloy, especially the treatment method of applying direct current under the condition of rare earth salt treatment liquid. Background technique [0002] Soak the aluminum alloy in CeCl 3 Or other rare earth metal chloride solution can form aluminum alloy rare earth conversion coating. This film can inhibit pitting corrosion, stress corrosion, crevice corrosion and corrosion fatigue of aluminum alloy in chlorine-containing medium. Its corrosion resistance is better than that of chromate conversion coatings (see Hinton BR et al. Cerium Conversion Coatings for the Corrosion Protection of Aluminum, Materials Forum, 1986, 19(3): 162). At present, there are three main methods for the rare earth conversion coating process, one of which is the chemical soaking method, which is characterized by adding H 2 o 2 , KMnO 4 , (NH 4 ) 2 S 2 o 8 Such strong o...

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Problems solved by technology

The disadvantage is that the formed conversion film is thin and the oxidant is unstable, which is not conducive to actual production; the second is the rare earth bohmite layer process, adding a small amount of triethanolamine or sodium fluoride to hot water, putting the aluminum alloy in it and boiling for a short time In this way, a bohmite layer is first formed on the surface, and then soaked in a rare earth salt solution, taken out and dried to obtain a rare earth conversion film. The disadvantage is that the treatment temperature is too high and the process is difficult to maintain (see Xingwen "Aluminum Metal Base Rare Earth Conversion Coating on the Surface of Composite Materials", "Surface Technology" 2000, 29(4): 1-4); the third is the process of combining chemical and electrochemical methods, which is rarely introduced at present, and the most typical one is Mansfeld et al. The researched "stainless aluminum" process: first in hot 10mMCe (NO 3 ) 3 (100°C) for two hours, then in 5mM hot CeCl 3 Immerse in solution (100°C) for two hours; in 0.1M deoxy Na 2 MoO 4 In the solution, for the aluminum alloy sample at the potential +500mV VSSCE Anodized for two hours

This process requires a long working time and high working temperature, so it is difficult to apply in actual industrial production

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