CN1453394A - Iron and steel surface sensitizing and blackening agent and relevant blackening process - Google Patents

Abstract

The iron and steel surface sensitizing and blackening agent includes sensitizing agent and normal temperature blackening liquid. Its formula is as follows: the sensitizing agent consists of CuSO4.5H2O, NiSO4.7H2O, sodium citrate, tartaric acid, amido sulfonic acid and water, and has pH value of 2-4; and the normal temperature blackening liquid consists of sodium sulfide, ethanol and water, and has pH value of 8-10. The blackening process includes the main steps of: pre-treatment of iron and steel parts, soaking the pre-treated iron and steel parts in the sensitizing agent liquid for 2-6 to sensitize, and soaking the sensitized and washed iron and steel parts in the normal temperature blackening liquid for 3-5 min to form black film.

Description

Steel surface sensitizing blackening agent and blackening process using same

The technical field is as follows:

the invention relates to the technical field of metal surface chemical treatment, in particular to a steel normal-temperature non-toxic blackening agent for carrying out chemical oxidation blackening on the surface of steel and a blackening process method using the blackening agent.

Secondly, background art:

the technology of forming an oxide film on the surface of steel by using a blackening agent is widely applied to the industries of machinery, weapons, clocks and the like. The traditional steel blackening is carried out in alkaline sodium nitrite solution at 135-150 ℃, the treatment time is long, the energy consumption is high, the pollution is heavy, the efficiency is low, the working environment is poor, and the iron blackening method is extremely unfavorable for the bodies of operators; the method leads a plurality of researchers to develop research work on the normal-temperature steel blackening process in recent years, and provides a plurality of blackening agents and blackening processes, but most of the developed blackening agents contain selenite which is a toxic substance and is easy to cause harm to human bodies and pollution to the environment; in addition, the adopted process method mostly adopts a one-step blackening method of blackening liquid, and the film forming quality is not high enough.

Thirdly, the invention content:

the technical problem to be solved by the invention is as follows: the problems that the existing normal-temperature steel blackening agent is toxic or the blackening liquid is not stable enough, and the adhesion force of a surface film layer generated by blackening is poor and the corrosion resistance is low are solved, and the steel surface sensitization rapid blackening agent which is used at normal temperature, has no pollution in the surface blackening processand discharge, has no peculiar smell in the solution and is nontoxic and harmless to human bodies and the blackening process method using the sensitization blackening agent are provided.

The technical scheme is as follows:

a normal temperature steel surface sensitization blackening agent comprises sensitization liquid and normal temperature blackening liquid, and the formula is as follows:

① sensitizing solution:

CuSO₄·5H₂O：4～10g/l NiSO₄·7H₂O：1～5g/l

sodium citrate: 4-10 g/l tartaric acid: 4 to 10g/l

Sulfamic acid: 4-10 g/l H₂O: balance of

pH＝2～4

② blackening liquid at normal temperature:

sodium sulfide: 40-100 g/l ethanol: 20 to 50ml/l

H₂O: balance of

pH＝8～10

A blackening process method using a normal-temperature steel surface sensitizing blackening agent is characterized by comprising the following steps: the method comprises the following technical processes:

① pretreating, namely, removing oil, pickling and rinsing on the surface of the steel part;

② sensitization, namely immersing the pretreated steel piece into the sensitization liquid of the normal temperature steel surface sensitization blackening agent for 2-6 minutes at normal temperature for sensitization;

③ washing with water, namely washing the sensitized steel piece with water;

④ blackening, namely soaking the cleaned steel piece in the blackening liquid for 3-5 minutes at normal temperature;

⑤ cleaning, namely cleaning the blackened steel piece with water;

⑥ post-treatment, namely sealing the cleaned blackening piece and soaking the blackening piece in dehydrated antirust oil to further improve the corrosion resistance of the blackening piece.

The invention has the following advantages:

1. the film layer has stable components and good adhesive force; copper sulfate in the sensitizing solution is a main film forming agent, nickel sulfate is an auxiliary film forming agent, and when the steel part reacts with the main film forming agent, an auxiliary film forming reaction is spontaneously generated, so that the composition and the structure of the film are changed, and the performances of the blackening film, such as corrosion resistance, adhesive force and the like, are improved. In the invention, the sodium citrate is used as a complexing agent and a stabilizing agent, and tartaric acid and sulfamic acid are also added as a complexing agent and a stabilizing agent, so that the complexing effect is further enhanced, and the performance of the solution is stabilized; the film forming reaction speed is adjusted, so that the film forming speed is higher and the film quality is better.

The blackening agent of the invention is divided into sensitizing solution and blackening solution, and the film forming mechanism thereof comprises the following steps:

(1) the iron matrix and the copper ions are subjected to a displacement reaction:

(2) sodium sulfide salt and the like react with Fe and Cu to generate black substances, and a black film is formed:

(3) fe produced by the reaction²⁺O in air₂React to produce Fe³⁺Conversion to Fe₃O₄：

Through detection and analysis, the film components contain S, Fe, Cu and O, and the film components blackened at normal temperature are not simple Fe₃O₄Since FeS, CuS, etc. are also contained, the film layer is stable.

In addition, the blackening process is divided into two steps, the sensitizing solution is acidic, the blackening solution is alkaline, and the blackening process is cleaned for the first time after sensitization to remove residual H on the surface of the steel part⁺Then, the film is put into an alkaline blackening solution for blackening so that the generated salt is more stable, and the quality of the film is higher.

And (3) carrying out a performance test, wherein ① carrying out a copper sulfate drop test shows that no color change, copper spots and rust spots appear within 40 seconds and completely meet the provisions of an electromechanical part standard WJ535-82, ② carrying out a test by using a 3% sodium chloride solution, and soaking the blackened part for 3 hours at 15-20 ℃ without contact spots and rust spots.

2. The blackening agent does not contain selenate, phosphoric acid and phosphate, and the blackening agent and the discharge are nontoxic, odorless and free of pungent smell;

fourthly, explanation of the attached drawings:

the invention relates to a blackening process flow chart

The fifth embodiment is as follows:

example (b):

a normal temperature steel surface sensitization blackening agent comprises sensitization liquid and normal temperature blackening liquid, and the formula is as follows:

① sensitizing solution:

CuSO₄·5H₂O：4～10g/l NiSO₄·7H₂O：1～5g/l

sodium citrate: 4-10 g/l tartaric acid: 4 to 10g/l

Sulfamic acid: 4-10 g/l H₂O: balance of

pH＝2～4

② blackening liquid at normal temperature:

sodium sulfide: 40-100 g/l ethanol: 20 to 50ml/l

H₂O: balance of

pH＝8～10

A process method for applying the normal-temperature steel surface sensitizing blackening agent to steel surface blackening is characterized by comprising the following steps: the method comprises the following technical processes:

① pretreating, namely, removing oil, pickling and rinsing on the surface of the steel part;

② sensitization, namely immersing the pretreated steel piece into the sensitization liquid of the normal temperature steel surface sensitization blackening agent for 2-6 minutes at normal temperature for sensitization;

③ washing with water, namely washing the sensitized steel piece with water;

④ blackening, namely soaking the cleaned steel piece in the blackening liquid for 3-5 minutes at normal temperature;

⑤ cleaning, namely cleaning the blackened steel piece with water;

⑥ post-treatment, namely sealing the cleaned blackening piece and soaking the blackening piece in dehydrated antirust oil to further improve the corrosion resistance of the blackening piece.

The normal temperature of the technological process refers to the temperature of 15-35 ℃, and the temperature is low, the reaction speed is slow, the temperature is high, and the reaction speed is high.

Claims (2)

1. A normal temperature steel surface sensitization blackening agent is characterized in that: the blackening agent comprises sensitizing solution and normal-temperature blackening solution, and the formula of the blackening agent is as follows:

① sensitizing solution:

CuSO₄·5H₂O：4～10g/l NiSO₄·7H₂O：1～5g/l

sodium citrate: 4-10 g/l tartaric acid: 4 to 10g/l

Sulfamic acid: 4-10 g/l H₂O: balance of

pH＝2～4

② blackening liquid at normal temperature:

sodium sulfide: 40-100 g/l ethanol: 20 to 50ml/l

H₂O: balance of

pH＝8～10

2. The blackening process method using the normal-temperature steel surface sensitizing blackening agent as claimed in claim 1, is characterized in that: the method comprises the following technical processes:

① pretreating, namely, removing oil, pickling and rinsing on the surface of the steel part;

② sensitization, namely immersing the pretreated steel piece into the sensitization liquid of the normal temperature steel surface sensitization blackening agent for 2-6 minutes at normal temperature for sensitization;

③ washing with water, namely washing the sensitized steel piece with water;

④ blackening, namely soaking the cleaned steel piece in the blackening liquid for 3-5 minutes at normal temperature;

⑤ cleaning, namely cleaning the blackened steel piece with water;

⑥ post-treatment, namely sealing the cleaned blackening piece and soaking the blackening piece in dehydrated antirust oil to further improve the corrosion resistance of the blackening piece.