What are the key steps to pay attention to during the blackening surface treatment process in Dalian

1、 Pre processing stage

1. Surface cleaning

Pre treatment is one of the more critical steps in the blackening process, which directly affects the final treatment effect. The surface of the workpiece must be thoroughly cleaned of oil stains, rust, and other impurities.

Oil removal treatment: Use alkaline oil remover or organic solvent to remove surface grease, usually controlled at 60-80 ℃ for 10-30 minutes

Acid pickling and rust removal: Use hydrochloric acid or sulfuric acid solution to remove oxide scale and rust, with a concentration of generally 10-20%, and the time depends on the degree of rust

Washing: After each chemical treatment, it must be thoroughly rinsed with clean water to avoid cross contamination of chemical residues

2. Surface activation

For certain metal materials, activation treatment is required to enhance surface activity:

Stainless steel and other materials require acid washing activation

Aluminum alloys usually require alkali corrosion treatment

Immediately perform blackening treatment after activation to avoid surface re oxidation

2、 Blackening stage

1. Solution preparation

The preparation of blackening solution directly affects the treatment effect:

Strictly prepare the solution according to the process requirements and control the proportion of each component

Common blackening agents include alkaline blackening agents, room temperature blackening agents, etc

The newly prepared solution needs to be matured to allow all components to fully react

2. Process parameter control

The process parameters during the blackening process must be strictly controlled:

Temperature control: High temperature blackening usually occurs at 130-150 ℃, while room temperature blackening occurs at 20-40 ℃

Time control: Typically 5-30 minutes depending on the material and requirements

PH value: Alkaline blackening pH value 11-13, requires regular testing and adjustment

Solution concentration: Regularly monitor and supplement to maintain the concentration of active ingredients

3. Mixing and moving

To ensure uniformity of processing:

Large workpieces need to be moved or rotated appropriately

The solution should be stirred moderately, but avoid vigorous stirring

Maintain appropriate spacing between workpieces to avoid overlap

3、 Post processing stage

1. Water washing and neutralization

After blackening treatment:

Immediately rinse with flowing water to remove residual medication

Neutralization treatment should be carried out if necessary, especially for acidic residues

Water quality requirements: Use deionized water or purified water

2. Closed treatment

To improve the protective performance of the black film:

Can be treated with oil immersion, wax coating, or specialized sealing agents

Oil immersion temperature 60-80 ℃, time 5-10 minutes

After sealing, drain appropriately to avoid oil accumulation

3. Drying

Timely drying to prevent water stains and secondary oxidation

The drying temperature should not be too high, generally 80-100 ℃

Pay attention to cleanliness when blowing compressed air dry

4、 Quality control

1. Appearance inspection

Color uniformity: It should be a uniform black or blue black color

Surface smoothness: There should be no white spots, flower spots, or rust stains

Adhesion inspection: Use tape to test the adhesion of the film layer

2. Performance testing

Corrosion resistance test: salt spray test or wet heat test

Wear resistance test: friction test or hardness test

Film thickness measurement: usually requires 1-3 μ m

3. Solution maintenance

Regularly analyze the composition of the solution and replenish it in a timely manner

Filter and remove suspended impurities

Control the accumulation of heavy metal ions

5、 Safety and Environmental Protection

1. Safety protection

Operators are required to wear protective clothing, gloves, and goggles

Good ventilation on site to avoid the accumulation of acid mist

Complete emergency equipment: eye wash stations, first aid kits, etc

2. Wastewater treatment

Classify and collect wastewater for treatment, and neutralize acidic and alkaline wastewater

Heavy metal wastewater needs to be treated specifically to meet standards before being discharged

Hand over the waste liquid to professional institutions for treatment

3. Equipment maintenance

Regularly check the heating system and ventilation system

Anti corrosion treatment of tank body to avoid leakage

Regular maintenance of pipelines, pumps, and valves

6、 Common Problems and Countermeasures

1. Uneven blackening film

Possible reasons:

Incomplete pre-processing

Insufficient stirring of the solution

Uneven temperature

Countermeasure:

Strengthen pre-processing

Improve solution circulation

Check the heating system

2. Poor adhesion of film layer

Possible reasons:

Insufficient surface activation

The blackening time is too short

Improper post-processing

Countermeasure:

Optimize activation process

Adjust the blackening time

Improve the closed process

3. Insufficient corrosion resistance

Possible reasons:

The membrane layer is not dense

Improper sealing treatment

Solution composition imbalance countermeasures:

Adjust blackening parameters

Strengthen the closure process

Analyze and adjust the solution

7、 Process optimization direction

Develop environmentally friendly blackening agents to reduce the use of heavy metals

Improve automation level and achieve precise control of process parameters

Develop composite processing technology, combining blackening with other surface treatment techniques

Develop blackening process suitable for new alloy materials

By strictly controlling the above key steps, the quality stability of blackening surface treatment can be ensured, meeting the requirements of different application scenarios for the surface performance of metal parts. In actual production, process adjustments and optimizations need to be made based on factors such as specific materials, workpiece shapes, and usage environments.