Process for corrosion-resistance passivation of ferrite stainless steel for packaging vehicle-mounted SCR

A passivation treatment, stainless steel technology, applied in the direction of metal material coating process, etc., can solve the problems of SCR system failure, inability to fully meet the chemical corrosion resistance requirements of vehicle-mounted SCR systems, vehicle failures and claims, etc., to improve life and significantly save money Benefits and social benefits, the effect of adding less

Active Publication Date: 2013-03-27
CHINA FIRST AUTOMOBILE +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Corrosion can disable the SCR system, eventually leading to vehicle failure and claims
[0008] For several commonly used stainless steel materials in the domestic market, such as austenitic SUS309 and SUS304, and ferritic 441, conventional chemical corrosion of urea reducing agent solution, high temperature and high pressure hydrothermal chemical corrosion test of urea reducing agent solution and simulation After the corrosion test of the condensing medium in the exhaust pipe, it is found that even the most high-grade and expensive austenitic SUS309 stainless steel cannot fully meet the chemical corrosion resistance requirements of the vehicle-mounted SCR system after packaging
[0009] How to solve the problem of chemical corrosion resistance of packaging materials for vehicle-mounted SCR systems has become an obstacle restricting the promotion and application of SCR technology in my country

Method used

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  • Process for corrosion-resistance passivation of ferrite stainless steel for packaging vehicle-mounted SCR
  • Process for corrosion-resistance passivation of ferrite stainless steel for packaging vehicle-mounted SCR
  • Process for corrosion-resistance passivation of ferrite stainless steel for packaging vehicle-mounted SCR

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0021] The three-way catalytic converter (TWC) system in my country has high corrosion and failure problems. Corrosion condensate from the TWC system was analyzed and found to contain NH 4 + , CO 3 2- , PO 4 3- , SO 4 2- , Cl - , NO 3 - , organic acids and other highly corrosive condensates.

[0022] Prepare the corrosive medium according to the proportion in Table 1, put it into the hydrothermal reaction container respectively, put several stainless steel metal test pieces, reserve 50% of the volume space of the reaction container, close the reactor, put it into a constant temperature box, and put it in a constant temperature box at a temperature of 80 °C. , the temperature inside the reaction vessel can reach more than 100 ℃, which is a gas-liquid mixture. The composition of the corrosive medium to simulate the condensate prepared in the test is shown in Table 1.

[0023] Table 1 Composition of corrosive medium for simulated condensate

[0024]

[0025] * No...

Embodiment 2

[0032] a) Weigh distilled water in a corrosion-resistant container, heat it to 50°C, put in 4 parts of phosphoric acid, 0.05 part of nitric acid, and 0.5 part of acetic acid, and stir evenly;

[0033] b) adding 4 parts of aluminum dihydrogen phosphate with a content of 50% wt into a), stirring until completely dissolved;

[0034] c) adding 0.05 part of chromium nitrate and 0.005 part of zinc nitrate into b), stirring until completely dissolved; heating to make the temperature of the liquid reach 90 ° C;

[0035] A commercially available domestic ferritic stainless steel material, that is, a steel plate with a thickness of 1.5 mm, is first subjected to degreasing treatment, and then placed in the prepared passivation treatment solution c) at a temperature of 90°C for 12 minutes. Take out the passivated ferritic stainless steel material from the passivation solution c), wash with distilled water, and air dry to complete the chemical corrosion-resistant passivation treatment on t...

Embodiment 3

[0040] The samples of ferritic stainless steel 441 were first degreased and dried.

[0041]The passivation treatment liquid is as follows in the following proportions: 6 parts of phosphoric acid, 0.1 part of nitric acid, 0.5 part of acetic acid, 6 parts of 50% wt aluminum dihydrogen phosphate, 0.1 part of chromium nitrate, 0.01 part of zinc nitrate, and the remaining weights are distilled water, heated and stirred. , dissolve, complete the preparation. The ferritic stainless steel 441 sample was immersed and passivated in the above-mentioned passivation solution for 10 min at 95°C. Condensate corrosion medium was prepared according to the ratio of Table 1 of Example 1, and the passivation was completed according to the test conditions in Example 1. The treated ferritic stainless steel material was subjected to corrosion resistance test, and the results are shown in Table 4.

[0042] Table 4 Corrosion resistance test results of ferritic stainless steel 441 after passivation

...

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Abstract

The invention relates to a process for the corrosion-resistance passivation of ferrite stainless steel for packaging vehicle-mounted SCR, which is to perform the surface treatment of a merchant ferrite stainless steel material in passivation solution. The chemical treatment solution comprises 4 to 10 portions of phosphoric acid, 0 to 0.1 portion of nitric acid, 0.5 to 1 portion of acetic acid, 4 to 6 portions of aluminium dihydrogen phosphate, 0.05 to 0.1 portion of chromic nitrate, 0 to 0.01 portion of zinc nitrate and the balance of distilled water, wherein the content of the aluminium dihydrogen phosphate is 50 weight percent. The process can obviously improve the resistances of the stainless steel to the high-temperature chemical corrosion by a urea reducer used by a vehicle-mounted SCR system and the resistance to the high-temperature chemical corrosion by corrosive atmosphere in exhausted gases and can reduce system material cost and prolong system service life after being used in the vehicle-mounted SCR system. The process creates significant economic and social benefits.

Description

Technical field: [0001] The invention relates to a corrosion-resistant passivation treatment process of ferritic stainless steel for vehicle-mounted SCR packaging, and the technology is applied to the post-treatment industry of automobile exhaust gas. Background technique: [0002] Over the next few years, automakers around the world, especially in the United States and Europe, will have to implement some more stringent specifications, such as Euro 5 and Euro 6 emission standards, on vehicle nitrogen oxide NOx and particulate PM emissions compliance. [0003] Under the pressure of emission regulations, on the one hand, foreign heavy-duty diesel engines for vehicles are constantly undergoing technical upgrades and improvements; , DPF (Diesel Particulate Filter) particle trap, DOC (Diesel OxidationCatalyst) oxidation catalyst and so on. [0004] The essence of SCR technology is to use urea to decompose NH at high temperature 3 , NH as reducing agent 3 and NO in engine exhau...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C23C22/07
Inventor 张克金张苡铭潘艳春夏琦
Owner CHINA FIRST AUTOMOBILE
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