Process for cathode electrolytic deposition of rare-earth conversion film

A technology of electrolytic deposition and chemical conversion film, which is applied in the field of processing with external direct current, can solve the problems of difficult maintenance of the process, high working temperature, and difficult application, and achieves improved hydrophilicity, improved corrosion resistance, and good binding force Effect

Inactive Publication Date: 2006-11-08
BEIJING UNIV OF CHEM TECH
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  • Description
  • Claims
  • Application Information

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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

Method used

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  • Process for cathode electrolytic deposition of rare-earth conversion film
  • Process for cathode electrolytic deposition of rare-earth conversion film
  • Process for cathode electrolytic deposition of rare-earth conversion film

Examples

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Embodiment 1

[0027] Embodiment 1. Cathodic electrolytic deposition process of antirust aluminum LF21

[0028] 1.1. The aluminum alloy adopts the anti-rust aluminum alloy of the national standard LF21 aluminum alloy. The test piece is subjected to pre-treatments such as grinding, degreasing, pickling, and alkali washing in sequence. The treatment process is: use water-resistant sandpaper to polish to 800# in sequence → deionized water washing → degreasing with acetone solution → deionized water washing → Na 2 CO 3 、Na 3 PO 4 Washing with mixed solution → washing with deionized water → alkaline washing with 50g / l NaOH solution → washing with deionized water → pickling with 200g / l nitric acid solution → washing with deionized water → drying.

[0029] 1.2. Preparation containing CeCl 3 、H 2 o 2 , The processing solution of citric acid is poured in the beaker in the water bath. and heated to 50°C, the ratio of the treatment solution is: CeCl 3 10g / l,H 2 o 2 60ml / l, corrosion inhibi...

Embodiment 2

[0033] Embodiment 2. Cathodic electrolytic deposition process of antirust aluminum LF21

[0034] The aluminum alloy adopts the anti-rust aluminum alloy of the national standard LF21 aluminum alloy. Cathodic electrodeposition treatment at 40°C, CeCl 3 20g / l,H 2 o 2 70ml / l, corrosion inhibitor citric acid 2.5g / l. All the other operating methods and process conditions are the same as in Example 1. The resulting Nyquist diagram is shown in Figure 4 . It can be seen from the figure that the arc radius of the conversion coating sample under electrochemical conditions is larger than that of the conversion coating and blank samples prepared under chemical impregnation conditions. It shows that the corrosion resistance of aluminum alloy is greatly improved after electrochemical treatment.

Embodiment 3

[0035] Embodiment 3. Cathodic electrolytic deposition process of antirust aluminum LF21

[0036] The aluminum alloy adopts the anti-rust aluminum alloy of the national standard LF21 aluminum alloy. Cathodic electrodeposition treatment at 60°C, CeCl 3 15g / l,H 2 o 2 65ml / l, corrosion inhibitor citric acid 2.3g / l. All the other operating methods and process conditions are the same as in Example 1. The resulting Nyquist diagram is shown in Figure 5 . It can be seen from the figure that the arc radius of the conversion coating sample under electrochemical conditions is larger than that of the conversion coating and blank samples prepared under chemical impregnation conditions. It shows that the corrosion resistance of aluminum alloy is greatly improved after electrochemical treatment.

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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...

Claims

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Application Information

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IPC IPC(8): C25D11/00C25D3/54
Inventor 左禹石铁赵景茂张晓丰
Owner BEIJING UNIV OF CHEM TECH
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