PRETREATMENT METHOD OF ALUMINUM ALLOY COIL

Abstract

The invention relates to the technical field of aluminum alloy surface treatment, in particular to the technical field of IPC C23C, and more specifically to a pretreatment method of an aluminum alloy coil. The invention can improve adhesion of an adhesive and weldability of an aluminum alloy at the same time through a specific pretreatment method combined with a specific treatment solution, and an aluminum alloy substrate after pretreatment has good compatibility with subsequent permanent anti-corrosion treatment, so that the pretreatment method is very suitable for welding or bonding of aluminum alloy parts of automobile bodies.

Claims

1. A pretreatment method of an aluminum alloy coil, comprising: S1 cleaning a surface of the aluminum alloy coil; S2 washing the surface of the aluminum alloy coil with deionized water; S3 treating the surface of the aluminum alloy coil with a treatment solution; S4 washing the surface of the aluminum alloy coil with deionized water; and S5 drying.

2. The pretreatment method of an aluminum alloy coil according to claim 1, wherein a material of the aluminum alloy coil comprises any one of 1XXX series aluminum alloy, 2XXX series alloy, 3XXX series aluminum alloy, 4XXX series aluminum alloy, 5XXX series aluminum alloy, 6XXX series aluminum alloy and 7XXX series aluminum alloy.

3. The pretreatment method of an aluminum alloy coil according to claim 1, wherein the cleaning in the step S1 is either a one-step method or a two-step method.

4. The pretreatment method of an aluminum alloy coil according to claim 3, wherein the two-step method comprises: degreasing the aluminum alloy coil with a degreasant, washing it with water, and then etching the coil with an etchant.

5. The pretreatment method of an aluminum alloy coil according to claim 4, wherein the degreasant comprises an alkaline degreasant and water; a weight of the alkaline degreasant is 1-7 wt % of the degreasant; the alkaline degreasant comprises a phosphorus-containing inorganic salt, potassium carbonate, a chelating agent and a non-ionic surfactant.

6. The pretreatment method of an aluminum alloy coil according to claim 4, wherein a use temperature of the etchant is 20-70? C.; an etching rate during the etching is 0.1-0.5 g/m.sup.2; the etchant is an aqueous solution of a mixture of an inorganic acid, a fluoride and a non-ionic surfactant.

7. The pretreatment method of an aluminum alloy coil according to claim 1, wherein the treatment solution in the step S3 is a phosphonic compound solution; a content of a phosphonic compound in the phosphonic compound solution is 0.0001-0.1 mol/L.

8. The pretreatment method of an aluminum alloy coil according to claim 7, wherein the phosphonic compound consists of phosphonic compounds with one or more structures of (OH).sub.2OP(CH.sub.2).sub.XPO(OH).sub.2, and (CH.sub.2).sub.X is a saturated straight-chain alkyl group, wherein X is 8-16.

9. The pretreatment method of an aluminum alloy coil according to claim 7, wherein treatment time of the phosphonic compound solution is 3 s-60 s; a pH value of the phosphonic compound solution is 1.5-6.5.

10. An application of the pretreatment method of an aluminum alloy coil according to claim 1, wherein the pretreatment method is applied to an automotive field.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0055] FIG. 1 shows an aluminum alloy surface treated by a pretreatment method of Embodiment 2 (right) and Comparative example 1 (left).

DESCRIPTION OF THE EMBODIMENTS

Embodiments

Embodiment 1

[0056] Embodiment 1 provides a pretreatment method of an aluminum alloy coil, including: [0057] S1. cleaning a surface of the aluminum alloy coil; [0058] S2. washing the surface of the aluminum alloy coil with deionized water; [0059] S3. treating the surface of the aluminum alloy coil with a treatment solution; [0060] S4. washing the surface of the aluminum alloy coil with deionized water; and [0061] S5. drying.

[0062] A material of the aluminum alloy coil is AA5005 aluminum alloy.

[0063] The cleaning in the step S1 is a two-step method.

[0064] A specific implementation of the two-step method is as follows: degreasing the aluminum alloy coil with a degreasant, washing it with water, and then etching the coil with an etchant.

[0065] A use temperature of the degreasant is 50? C.

[0066] The degreasant is an alkaline degreasant and water.

[0067] The alkaline degreasant is 5 g/L potassium pyrophosphate, 5 g/L sodium tripolyphosphate, 5 g/L potassium carbonate, 2.0 g/L sodium gluconate and 1.0 g/L non-ionic surfactant.

[0068] The non-ionic surfactant is a fatty alcohol polyether non-ionic surfactant.

[0069] A hydroxyl value of the fatty alcohol polyether non-ionic surfactant is 85-95 mg KOH/g, and a cloud point (1% solution) is 28-31? C.

[0070] The fatty alcohol polyether non-ionic surfactant is Dehypon LS 54 produced by BASF.

[0071] A use temperature of the etchant is 28? C.

[0072] An etching rate during the etching is 0.1 g/m.sup.2.

[0073] The etchant is an aqueous solution of a mixture of an inorganic acid, a fluoride and a non-ionic surfactant.

[0074] The etchant is 6 g/L 98 wt % sulfuric acid, 0.4 g/L 98 wt % ammonium hydrogen fluoride and 0.25 g/L non-ionic surfactant.

[0075] A conductivity of deionized water in the step S2 is less than 50 ?s/cm.

[0076] The treatment solution in the step S3 is a phosphonic compound solution.

[0077] A content of an organic phosphorus compound in the organic phosphorus compound solution is 0.0006 mol/L.

[0078] A structure of the phosphonic compound is (OH).sub.2OP(CH.sub.2).sub.XPO(OH).sub.2, and (CH.sub.2).sub.X is a saturated straight-chain alkyl group, wherein X is 12.

[0079] A use temperature of the phosphonic compound solution is 55? C.

[0080] Treatment time of the phosphonic compound solution is 30 s.

[0081] A pH value of the phosphonic compound solution is 3.

[0082] The treating of the step S3 is dipping.

[0083] Dipping time of the step S3 is 30 s.

[0084] A conductivity of deionized water in the step S4 is less than 50 ?s/cm.

[0085] A drying temperature PMT of the step S5 is 80? C.

[0086] Drying time of the step S5 is 10 min.

Embodiment 2

[0087] Embodiment 2 provides a pretreatment method of an aluminum alloy coil, and the specific implementation is the same as that of Embodiment 1. The difference is that an etching rate during the etching is 0.2 g/m.sup.2.

Embodiment 3

[0088] Embodiment 3 provides a pretreatment method of an aluminum alloy coil, and the specific implementation is the same as that of Embodiment 1. The difference is that an etching rate during the etching is 0.3 g/m.sup.2.

Comparative Example 1

[0089] Comparative example 1 provides a pretreatment method of an aluminum alloy coil, and the specific implementation is the same as that of Embodiment 2. The difference is that the treatment solution in the step S3 is the treatment solution recorded in the US Patent MS00602003OA, a phosphorus content in the treatment solution is 1.5 g/L, a temperature of a bath solution is 55? C., a pH of the bath solution is 1.5, and dipping time is 30 s.

Comparative Example 2

[0090] Comparative example 2 provides a pretreatment method of an aluminum alloy coil, and the specific implementation is the same as that of Embodiment 2. The difference is that the treatment solution in the step S3 is the treatment solution GB X4591A2 recorded in the US Patent MS006562148B, a concentration of the treatment solution in a bath solution is 50 g/L, a temperature of the bath solution is 28? C., a pH of the bath solution is adjusted to 3.8 with GBA H7271, and dipping time is 6 s.

Embodiment 4

[0091] Embodiment 4 provides a pretreatment method of an aluminum alloy coil, and the specific implementation is the same as that of Embodiment 2. The difference is that a content of an organic phosphorus compound in the organic phosphorus compound solution is 0 mol/L.

Embodiment 5

[0092] Embodiment 5 provides a pretreatment method of an aluminum alloy coil, and the specific implementation is the same as that of Embodiment 2. The difference is that a content of an organic phosphorus compound in the organic phosphorus compound solution is 0.00015 mol/L.

Embodiment 6

[0093] Embodiment 6 provides a pretreatment method of an aluminum alloy coil, and the specific implementation is the same as that of Embodiment 2. The difference is that a content of an organic phosphorus compound in the organic phosphorus compound solution is 0.0003 mol/L.

Embodiment 7

[0094] Embodiment 7 provides a pretreatment method of an aluminum alloy coil, and the specific implementation is the same as that of Embodiment 2. The difference is that a content of an organic phosphorus compound in the organic phosphorus compound solution is 0.001 mol/L.

Embodiment 8

[0095] Embodiment 8 provides a pretreatment method of an aluminum alloy coil, and the specific implementation is the same as that of Embodiment 2. The difference is that a content of an organic phosphorus compound in the organic phosphorus compound solution is 0.0015 mol/L.

Performance Test Method

1. Surface Resistance Performance Test

[0096] The surface resistance of the pretreated aluminum alloy coils using the aluminum alloy coils described in Embodiments 1-3 and Comparative examples 1-2 is measured, and the pretreated aluminum alloy coils continue to be measured for the surface resistance after being kept at 85? C. and 85% humidity for 15 days, and the measurement results are recorded in Table 1.

TABLE-US-00001 TABLE 1 Surface resistance performance test data Surface resistance ?? Initial After 15 days Embodiment 1 59 35 Embodiment 2 45 30 Embodiment 3 29 20 Comparative example 1 40 228 Comparative example 2 49 173

[0097] It can be seen from the resistance test that the aluminum alloy coil treated with the solution of the application can inhibit the growth of the surface oxide layer, thereby reducing the surface resistance and improving the subsequent welding performance. It can be seen from solutions 1-3 that the amount of pickling etching increases, the surface resistance value decreases, but a higher etching amount consumes more chemicals, which increases the cost of pretreatment.

2. Wettability Test

[0098] Wettability test: a drop of pure water is dropped on the surfaces of the pretreated aluminum alloy coils using the aluminum alloy coils described in Embodiment 2 and Comparative example 1, and the wettability of pure water is observed. The results are shown in FIG. 1. It can be observed that the surface of Embodiment 2 is extremely hydrophobic, and the surface of Comparative example 1 is extremely hydrophilic in the application.

[0099] Copper sulfate color change test: a copper sulfate reagent is prepared, including 40 ml of 2% copper sulfate pentahydrate, 20 ml of 2% sodium chloride, 0.2 ml of 0.1 g/L hydrochloric acid, 0.8 ml of deionized water, and a pH of the solution is about 4.3. The copper sulfate reagent is dropped on the surfaces of the pretreated aluminum alloy coils using the aluminum alloy coils described in Embodiment 2, Comparative example 1, Embodiments 4-8. Color change time of copper sulfate is observed. The initial color of color change is: light blue; the end color is: reddish brown. The color change time is recorded in Table 2.

TABLE-US-00002 TABLE 2 Color change time of copper sulfate Color change time of copper sulfate/s Embodiment 2 75 Comparative example 1 35 Embodiment 4 35 Embodiment 5 50 Embodiment 6 73 Embodiment 7 75 Embodiment 8 75

[0100] It can be seen from the wettability test that the reason for the high surface resistance of the aluminum alloy coil after treatment of Comparative example 1 during storage may be that its surface is extremely hydrophilic, and the aluminum alloy coil after treatment of Embodiment 2 of the application has a long color change time, indicating that the corrosion resistance of the aluminum alloy coil pretreated by the method of the application is better than that of Comparative Example 1. As the content of a phosphonic compound in the phosphonic compound solution increases, the color change time of copper sulfate tends to be stable, indicating that the content of the phosphonic compound has a limited influence on the color change time of copper sulfate, and the excessively high content of phosphonic will increase the cost.

3. Adhesive Performance Test

[0101] For the pretreated aluminum alloy coils (AA6016) using the aluminum alloy coils described in Embodiment 2 and Comparative Example 1, the shear strength and T-peel strength between it and epoxy structural adhesive TEROSON EP 5089 are tested. The test conditions are 720 h of salt spray and 10 days after 54? C. water, respectively. The test method of shear strength is: single lap joint, bonding area 25*12.5*0.2 mm, tensile speed 10 mm/min. The test method of T-peel strength is: single lap joint, bonding area 25*100*0.2 mm, stretching speed 50 mm/min. The results are recorded in Table 3.

TABLE-US-00003 TABLE 3 Adhesive performance test form Adhesive performance test Test results Embodiment Comparative Test items Test conditions 2 example 1 Shear strength Mpa Salt spray resistance 23.1 22.5 Water resistance 24 22.7 T-peel strength N/mm Salt spray resistance 7.5 7.1 Water resistance 7.3 6.6

[0102] It can be seen from Table 3 that the shear strength and T-peel strength between the aluminum alloy coil after pretreatment of Embodiment 2 of the application and the adhesive are high, and the adhesive performance is better than that of the aluminum alloy coil after treatment of Comparative example 1, indicating that the aluminum alloy coil surface treated by the application has excellent adhesion with the epoxy structural adhesive.

4. Compatibility Test

[0103] Phosphating pretreatment is carried out on Embodiment 2 and the unpretreated aluminum plate (AA5754), respectively, and then the morphology of a phosphating film is observed with the help of a scanning electron microscope to judge the compatibility with phosphating pretreatment. The process of phosphating pretreatment is as follows: degreasing with Gardoclean 5176 produced by Chemetall at 55? C. for 3 min, rinsing the surface with tap water, and adjusting the surface with Gardolene V6513 surface conditioner, after phosphating with Gardobond 2600 at 55? C. for 3 min, washing with water, and drying at 80? C. for 10 min. The results are recorded in Table 4.

TABLE-US-00004 TABLE 4 Compatibility test data Morphology of a phosphating film Embodiment 2 Pretreated test plate Closed, fine crystals Unpretreated test plate Closed, fine crystals

[0104] It can be seen from Table 4 that the surface morphology of the phosphating film formed after the phosphating pretreatment of the aluminum alloy coil after the pretreatment of the application is consistent with that after the phosphating treatment of the untreated aluminum alloy coil, indicating that the pretreated aluminum alloy substrate has good compatibility with the subsequent permanent anti-corrosion treatment, which makes the pretreatment method very suitable for the welding or bonding of the alloy parts of automobile bodies.