Application of Zinc-Nickel Alloy Technology in Long-term Anticorrosion of Coal Mine Fasteners

Application of Zinc-Nickel Alloy Technology in Long-term Anticorrosion of Coal Mine Fasteners Yi Chunlong, Ou Xuemei, Tang Dafang (China University of Mining and Technology, Xuzhou, Jiangsu 221008, China) The systematic study on the properties of zinc-nickel alloy coatings.

1 Overview The underground coal mine environment is harsh, the water quality is complex, and it is accompanied by various harmful gases such as sulfur dioxide. The fasteners in the mine are in a humid and corrosive environment for many years. The traditional methods of anti-corrosion fasteners such as galvanizing are used underground for 1 year. The left and right will rust and bite. With the successful application of long-lasting anti-corrosion technology of arc spraying on wellbore equipment, the long-term anti-corrosion problem of coal mine fasteners has become increasingly prominent, and the protection technology of fasteners has also put forward higher requirements.

At present, most of the protective treatment of fasteners adopts traditional processes such as galvanizing and hot-dip galvanizing. In the harsh environment, the corrosion resistance cannot meet the requirements. In severe cases, even corrosion leads to early failure and causes a safety accident. Therefore, it is of great significance to study the corrosion protection technology of fasteners.

(3) It is applied to the coal mine auxiliary wellhead yard, and replaces the manual cart with machinery to reduce the labor intensity. It can save 2 cart workers per shift, save the auxiliary operation time of the transfer operation, and improve the operation management and maintenance conditions.

(4) It can be used in the auxiliary shaft wellsite to be equipped with other equipment (: i99911, responsible editor: Wang Zongqi) 禹) the overall downhole requirements, with the characteristics of China's coal mines.

The turntable can enter the car in one direction, get out in two directions, or enter the car in two directions, and the requirements for getting out in one direction.

Depending on the requirements of the site layout, the drive unit of the design is below, and the drive unit can also be placed on top.

3 The continuity of the equipment's advanced nature. The mine car electric turntable makes the mine car run continuously when it is turning. Therefore, the mine car has a large passing capacity when turning, which shortens the cycle time of the mine car.

The 5t mine car can be transferred by the same equipment, which can greatly reduce the design work and other auxiliary workload. Reduce processing costs, facilitate equipment generalization, standardization and scientific management.

It is easy to apply microcomputer monitoring, realize mechanization, automatic management, and improve labor productivity.

It can be used in the underground horizontal parking lot of coal mines, which can reduce the length of the roadway by more than 100m and save construction funds.

The electric shaft carousel is used in the auxiliary shaft of the auxiliary shaft, which can reduce the floor space in the industrial square ring yard. This is especially important in the case of a limited range of industrial coal pillars.

The electric shaft carousel is used in the auxiliary shaft circulation yard to make the mine car not out of the wellhead and solve the problem of the frozen bottom in the alpine region.

Reducing the construction area and building volume of the wellhead housing is conducive to wellhead insulation.

The chief engineer of the project supervision, published many papers.

The amount of increase and increase of g plus 2 fasteners common anti-corrosion method comparison 21 electro-galvanized fastener zinc plating layer in coal mine environment anti-corrosion life is only 1 ~ 2 years. Although electro-galvanized has anti-corrosion effect on steel components, and it is still widely used today, with the continuous improvement of anti-corrosion requirements in the use environment, electro-galvanizing can no longer meet the needs.

The hot-dip galvanizing hot-dip galvanizing coating is thicker than electro-galvanized, and its corrosion resistance is higher than that of electro-galvanized. However, for fastener parts, the thickness of the coating cannot be increased infinitely due to the tolerance of the thread. Secondly, there is no chromate passivation film on the hot-dip galvanized surface, so that the corrosion-resistant life of the fastener parts using hot-dip galvanizing anti-corrosion is also short. Hot-dip galvanizing for fastener anti-corrosion also increases the complexity of the process: firstly, the fastener thread must have sufficient negative tolerance; secondly, because the immersion coating fills the thread, the threaded part needs to be threaded. It is also inevitable that the local zinc layer is removed and the substrate is exposed, resulting in failure of the local corrosion protection. The temperature of hot-dip galvanizing is above 300 °C. For some heat-treated parts, the material properties may change, resulting in changes in mechanical properties and affecting the use.

The formation principle of 23 Dacromet coating Dacromet coating is to dip the workpiece and bake at 300 °C to form a coating. It is a cathodic coating, which can resist neutral salt spray for more than 480h, and has good corrosion resistance. However, the Dacromet coating has a low hardness, and the Dacromet fastener is liable to cause coating scratches when colliding or screwing, resulting in a decrease in corrosion resistance. The Dacromet coating formation process requires that the workpiece be baked multiple times, which may cause changes in the mechanical properties of the part. Dacromet coating production equipment has a large investment and high processing cost.

With the development of industrial technology, the requirements for anti-corrosion technology and anti-corrosion coatings have been continuously improved. Zinc-nickel alloy coatings have begun to be applied. The zinc-nickel alloy coating features: zinc-nickel alloy (color blunt) coating has good corrosion resistance and is an anode long-lasting anti-corrosion coating.

The thickness of the coating is within the tolerance of the thread and the corrosion life can be doubled without changing the processing conditions of the fastener.

It has a certain wear resistance and hardness is higher than other anti-corrosion methods, so as to avoid damage to the plating layer when the thread is repeatedly unscrewed.

The coating has good thermal shock resistance, does not produce hydrogen embrittlement, and does not change the mechanical properties of the material.

The process is simple, the operation control is accurate, and the production cost is low. 3 Zinc-nickel alloy electrodeposition process 31 The formation of zinc-nickel alloy plating layer is formed by electroplating of zinc salt, nickel salt, conductive salt and additives. Abnormal co-deposition at the same polarization potential is a single C-phase zinc-nickel alloy coating. After passivation treatment, a highly corrosion-resistant zinc-nickel alloy plating layer is obtained. In order to meet different corrosion resistance and appearance requirements, a zinc-nickel alloy coating which is passivated by color, white or black can be obtained.

32 electrodeposition process pretreatment y degreasing + cleaning y derusting y cleaning y activation + water washing y electroplating zinc nickel alloy three-stage countercurrent rinsing y passivation y washing y dry y test y classification packaging.

33 plating solution and process conditions plating solution and process conditions are shown in Table 1. Table 1 plating solution and process conditions items color, white passivated black, white passivated conductive salt / gL-1 coating content /% remaining Zn coating thickness / Lm temperature / °c pH current density Dk (hang plating) (roll plating) (hang plating) (roll plating) 4 zinc-nickel alloy coating properties study coating appearance. The coating is bright silver white and can have white, five-color, black passivation film.

85, through the steel ball friction polishing test (suitable for thin coating), scribing cross-hatch test, bending test, tensile test, the coating has no peeling, peeling phenomenon.

Coating thickness. The thickness of the coating has a significant effect on the corrosion resistance. The thickness of the coating is generally 5~ the hardness of the coating according to the size and corrosion resistance of the fastener. The Vickers hardness of zinc-nickel alloy coatings with different nickel contents was measured by M-type micro hardness tester. The results are shown in Table 2. It is found that the hardness of zinc-nickel alloy coating is higher than that of galvanizing, and zinc with different nickel content in Table 2 Nickel alloy coating hardness coating nickel content /% coating hardness / HV coating nickel content and passivability. The zinc-nickel alloy coatings studied in this process were simultaneously measured by S250Mk3 scanning electron microscope, chemical gravimetric method and spectrophotometric colorimetric method. The measurement results of the same batch of samples were basically the same. The coatings with different zinc-nickel contents are controlled according to different corrosion resistance and passivation color requirements.

The coating is resistant to thermal shock. The zinc-nickel alloy coating sample is heated to a set temperature in an oven, and immediately immersed in room temperature water for chilling after taking out, and the coating is not pelt, non-bubble, or detached, and the thermal shock of the zinc-nickel alloy coating is investigated. performance. Test results Zinc-nickel alloy coating has a thermal shock resistance temperature of up to 250, and the sample shows bubbling and peeling, but the sample still has no bubbling or peeling when slowly cooling.

Zinc-nickel alloy coating corrosion resistance. Zinc-nickel alloy coating provides cathodic protection for fasteners and has excellent corrosion resistance. The coating of zinc-nickel alloy and the like was subjected to weak polarization to measure the corrosion current density in a 5% NaCl solution, and a neutral salt spray was used. The test confirmed that the corrosion resistance of the zinc-nickel alloy coating is related to the nickel content of the coating, and the corrosion resistance of the Zn-Zn-nickel alloy coating is the best. The equipment used in the test was CMB-1510B instantaneous corrosion rate measuring instrument and DF-27 type multi-purpose corrosion test box.

Table 3 Corrosion current and neutral salt spray test results of different nickel content coatings Plating type Coating thickness / L Passivation film Corrosion current density Neutral salt spray Red rust time / h Electroplating Zn color blunt hot dip Zn color blunt zinc nickel alloy Plating, hot dip galvanic corrosion current density as a function of time 1 a hot-dip galvanizing in brine; 2 - hot-dip galvanizing in tap water; 3 - zinc-nickel alloy in brine; 4 - zinc-nickel alloy in tap water. On-site hanging test at the Sanhejian Coal Mine of Xuzhou Mining Bureau and Yaoqiao Coal Mine of Datun Coal and Electricity Company has achieved good results. Has been successfully applied to Henan, Shandong, Liaoning, Gansu, Hebei, Jiangsu and other mines of various standard fasteners, U-bolts, washers, anchors, node clips, etc. more than 150 tons of electroplated zinc-nickel alloy anti-corrosion, use 3 ~ 4 years of good results, no rust. In addition, zinc-nickel alloy coatings have also been applied in automotive fasteners, guardrails, household appliances and electronic control equipment.

The corrosion current density of the 6-zinc-nickel alloy coating in the medium is much lower than that of the electro-galvanized layer and the hot-dip galvanized layer, and the corrosion-resistant life is long.

The high corrosion-resistant zinc-nickel alloy coating with low corrosion rate will be the development direction of long-term corrosion protection of steel parts with anodic coating. Its development trend is to replace electroplating zinc, hot dip galvanizing and cadmium plating.

In the mine environment and other industrial environments, zinc-nickel alloy coating is the preferred method for long-term corrosion protection of fasteners.