Magnesium alloy chromium-free fluorine-free phosphorization solution and phosphorization method

Abstract

The invention relates to magnesium alloy chromium-free fluorine-free phosphorization solution and a phosphorization method. Each liter of the magnesium alloy chromium-free fluorine-free phosphorization solution comprises 1 to 50 g of dihydric phosphate, 0 to 30 g of nitrate and 0.1 to 5 g of additive. The processed magnesium alloy workpiece is soaked and stood in the phosphorization solution of which the pH value is adjusted to be 2.0 to 5.0 by using phosphoric acid and ammonia water and is subjected to phosphating treatment at the temperature of between 30 and 100 DEG C for 1 to 60 minutes to form a phosphate coating. The magnesium alloy is phosphated by the phosphorization solution and the process, a uniform phosphate conversion coating with high corrosion resistance can be obtained on the surface of the magnesium alloy and the phosphate coating can effectively improve the adhesion and the protective property of the subsequent coatings. The phosphorization solution on the surface ofthe magnesium alloy has the advantages of few components and simple preparation. The phosphorization method of the phosphorization solution has the advantages of easy control, stable process, low cost and little sediment.

Description

technical field

[0001] The invention relates to a corrosion-resistant chromium-free and fluorine-free phosphating solution formula and a phosphating method on the surface of a magnesium alloy, belonging to the technical field of magnesium alloy surface anticorrosion treatment. Background technique

[0002] Magnesium alloy is known as "the most potential and promising green engineering material in the 21st century", and its density is small (1.8g / cm 3 Left and right), high specific strength, large elastic modulus, good shock absorption, and greater impact load capacity than aluminum alloys, it is more and more widely used in aviation, electronic communication, and automotive fields. However, due to the active chemical properties of magnesium, the electrode potential is very low (-2.34KV), resulting in poor corrosion resistance of magnesium alloys, which seriously hinders its promotion and application. Improving the corrosion resistance of magnesium alloys can be achieved by ...

Examples

Embodiment 1

[0039] Prepare the phosphating solution according to the following formula:

[0040] Manganese dihydrogen phosphate 40 g / L

[0041] Zinc nitrate 10 g / L

[0042] Citric acid 1 g / L

[0043] Sodium molybdate 1 g / L

[0044] The corrosion resistance of the phosphating film prepared by using the above formula phosphating solution was detected by pitting corrosion of copper sulfate solution. The specific treatment and performance are shown in Table 1.

[0045] Table 1

[0046]

[0047]

[0048] 5% (wt%) NaCl neutral salt spray test (NSS) and adhesion test (cross-hatch method) were carried out on the samples treated above with sprayed and unsprayed amino drying varnish. The test results are shown in Table 2.

[0049] Table 2

[0050]

Embodiment 2

[0052] Prepare the phosphating solution according to the following formula:

[0053] Zinc dihydrogen phosphate 20 g / L

[0054] Manganese nitrate 25 g / L

[0055] Sodium tartrate 3 g / L

[0056] Phytic acid 1 g / L

[0057] The corrosion resistance of the phosphating film prepared by using the above formula phosphating solution was detected by pitting corrosion of copper sulfate solution. The specific treatment and performance are shown in Table 3.

[0058] table 3

[0059]

[0060]

Embodiment 3

[0062] Prepare the phosphating solution according to the following formula:

[0063] Manganese dihydrogen phosphate 15 g / L

[0064] Citric acid 5 g / L

[0065] Sodium molybdate 5 g / L

[0066] The corrosion resistance of the phosphating film prepared by using the above formula phosphating solution was detected by pitting corrosion of copper sulfate solution. The specific treatment and performance are shown in Table 4.

[0067] Table 4

[0068]

technical field

[0001] The invention relates to a corrosion-resistant chromium-free and fluorine-free phosphating solution formula and a phosphating method on the surface of a magnesium alloy, belonging to the technical field of magnesium alloy surface anticorrosion treatment. Background technique

[0002] Magnesium alloy is known as "the most potential and promising green engineering material in the 21st century", and its density is small (1.8g / cm 3 Left and right), high specific strength, large elastic modulus, good shock absorption, and greater impact load capacity than aluminum alloys, it is more and more widely used in aviation, electronic communication, and automotive fields. However, due to the active chemical properties of magnesium, the electrode potential is very low (-2.34KV), resulting in poor corrosion resistance of magnesium alloys, which seriously hinders its promotion and application. Improving the corrosion resistance of magnesium alloys can be achieved by ...

Examples

Embodiment 1

[0039] Prepare the phosphating solution according to the following formula:

[0040] Manganese dihydrogen phosphate 40 g / L

[0041] Zinc nitrate 10 g / L

[0042] Citric acid 1 g / L

[0043] Sodium molybdate 1 g / L

[0044] The corrosion resistance of the phosphating film prepared by using the above formula phosphating solution was detected by pitting corrosion of copper sulfate solution. The specific treatment and performance are shown in Table 1.

[0045] Table 1

[0046]

[0047]

[0048] 5% (wt%) NaCl neutral salt spray test (NSS) and adhesion test (cross-hatch method) were carried out on the samples treated above with sprayed and unsprayed amino drying varnish. The test results are shown in Table 2.

[0049] Table 2

[0050]

Embodiment 2

[0052] Prepare the phosphating solution according to the following formula:

[0053] Zinc dihydrogen phosphate 20 g / L

[0054] Manganese nitrate 25 g / L

[0055] Sodium tartrate 3 g / L

[0056] Phytic acid 1 g / L

[0057] The corrosion resistance of the phosphating film prepared by using the above formula phosphating solution was detected by pitting corrosion of copper sulfate solution. The specific treatment and performance are shown in Table 3.

[0058] table 3

[0059]

[0060]

Embodiment 3

[0062] Prepare the phosphating solution according to the following formula:

[0063] Manganese dihydrogen phosphate 15 g / L

[0064] Citric acid 5 g / L

[0065] Sodium molybdate 5 g / L

[0066] The corrosion resistance of the phosphating film prepared by using the above formula phosphating solution was detected by pitting corrosion of copper sulfate solution. The specific treatment and performance are shown in Table 4.

[0067] Table 4

[0068]

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