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Guide for quality control of electroplating process

1 whole process control
The quality characteristics of plated parts are affected by the working quality of each link in the whole process, such as" low hydrogen embrittlement" Therefore, it is necessary to establish a quality control system for the whole process of material supply, pre-plating treatment, electroplating, post-plating treatment and finished product inspection.
2 Control Points
Beginning with the analysis of the general quality characteristics of plated parts, the key links affecting the quality of plated parts and the links with repeated quality problems are found out in the process flow, and control points are established for key control.Find out the main influencing factors and clearly define the control items, contents and methods.Generally, control points are set up in the links of raw material incoming inspection, etching, electroplating, hydrogen displacement and passivation.
3 Process Documentation
Different electroplated parts should prepare appropriate process documents according to their characteristics.Orthogonal test should be carried out actively for different process flow, composition and ratio of treatment solution and electroplating solution, electroplating process parameters (current density, working temperature, time, pH value, etc.) and operation methods, so as to find out the best process scheme, improve the process level and accumulate mature process experience.
4 Process materials
4.1 Strict quality standards must be established for chemical raw materials, metal anodes and other raw materials used in the process, and the specifications, grades, purity levels and the maximum allowable content of impurities of raw materials must be clearly defined.When the purity of commercial raw materials cannot meet the quality requirements, the detailed purification method and quality requirements shall be determined through tests.
4.2 The modification or substitution of raw materials shall be approved by the technical section chief and approved by the chief engineer or the factory director before being put into use after passing the small test, pilot test and small batch test of the technical department.
4.3 Raw materials purchased into the factory must go through strict acceptance of quality certification documents and sampling analysis and inspection, and can only be put into storage after passing the acceptance.
4.4 Raw materials shall be kept separately according to their properties.Raw materials of different specifications and purity shall not be mixed.Flammable and explosive chemical raw materials should have special management system and isolated storage system, and the storage warehouse should have ventilation and heat dissipation conditions that meet the requirements, and be equipped with corresponding fire control measures.Dramatic drugs used in electroplating should be stored in a special drama drug storehouse, which must be managed by double lock system, and one of them is in charge of the factory security department.Strict warehousing, storage and picking system should be established.
5 Pretreatment
5.1 The parts to be plated shall be accepted according to the technical requirements before plating, and those that do not meet the requirements shall be rejected.
5.2 In order to reduce the residual stress caused by machining, grinding, forming and cold straightening, For ferrous metal parts with tensile strength greater than or equal to 1034MPa to prevent cracking during electroplating, stress relief heat treatment must be carried out before plating, and the treatment temperature must be lower than the tempering temperature of this material (generally at least 30 ℃ lower than the tempering temperature), but not lower than the stress relief temperature.The treatment time depends on the type and grade of metal, and the corresponding temperature and time of stress relief heat treatment should be specified for materials with different strength levels in the process documents.
5.3 The interval time between sandblasting and electroplating must be strictly required.For high-strength steel with tensile strength above 1240MPa, the interval time shall generally not exceed 1h.
5.4 High-strength steel parts with tensile strength above 1240MPa, thin-walled parts and elastic parts are strictly prohibited from strong etching.
5.5 Cleaning after degreasing and etching should be arranged reasonably, and cleaning methods (such as countercurrent rinsing) should be improved to improve cleaning effect.
5.6 The cleaning quality of pretreatment before plating should be checked by the method of checking the continuity of water film, and the water film should be qualified if it does not break for 30s.
6 Bath fluid control
6.1 Bath fluid filtration should be based on the needs of specific process or production, using periodic filtration or continuous filtration.
6.2 All kinds of bath solutions such as pretreatment solution (such as acid and alkali solution), electrolyte and post-treatment solution (such as passivation solution) must be strictly controlled during use.It should be supplemented and adjusted according to the different consumption of various chemical raw materials.The analysis period of different bath solutions should be specified to keep the composition of bath solutions within the range specified by the process.When the analysis results of a solution exceed the specified range for two consecutive times, the analysis period should be shortened.
6.3 Daily maintenance of bath solution shall be strengthened, and a daily maintenance record system shall be established, which shall include the name of plating parts, plating area, coating thickness, process parameters, bath solution composition analysis results, charging conditions and bath solution troubleshooting, etc.
6.4 According to different bath solution, operation frequency, plating area, etc., Through laboratory tests and combined with the experience and data accumulated in long-term production practice, a replacement cycle is stipulated for the treatment solution without regeneration value, and a large treatment cycle is stipulated for the plating solution with regeneration value, so that the impurity content in the bath is controlled within the permitted range, and the performance of the bath solution is restored.
7 Post-treatment
7.1 According to the quality requirements of plated parts, the post-treatment processes such as cleaning, hydrogen displacement, light emission, passivation, drying and coating should be arranged reasonably.
7.2 For parts requiring hydrogen displacement, hydrogen displacement treatment must be carried out after plating.All ferrous metal parts with tensile strength greater than or equal to 1034MPa should be treated with hydrogen displacement after plating.Parts that need to be deplated and re-plated, deplated It should be treated by hydrogen flooding before; If there is a new hydrogen permeation phenomenon in the deplating process, hydrogen displacement treatment still needs to be added after deplating.For re-plated parts, hydrogen must be removed after plating.
7.3 For parts requiring hydrogen displacement after plating, hydrogen displacement treatment shall be carried out as soon as possible after plating.The interval between electroplating and hydrogen displacement treatment shall not exceed 4 hours for ferrous metal parts with tensile strength greater than 1240MPa and 10 hours for ferrous metal parts with tensile strength equal to or less than 1240MPa.
8 Finished product test
The appearance, coating thickness, adhesion and contact couple fit of the plated parts after plating in each bath shall be inspected and recorded.And make marks or labels at appropriate positions that do not affect the quality of plated parts.
Inspections and tests that are inconvenient to be carried out on plated parts are allowed to be carried out on templates plated under the same batch and process conditions.
9 Environmental conditions
Attention should be paid to the influence of environmental conditions on electroplating quality, continuous improvement of the operating environment of each electroplating process, strengthening ventilation, setting up equipment for removing harmful gases and dust, strengthening technical transformation, continuously reducing the labor intensity of operation and minimizing the influence of objective factors on quality.

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