In the process of electroplating, it is inevitable to occur various kinds of different faults, such as poor coating binding force, brittle, pinhole or burr, general point hair flower, burning black and low current density area is not bright.
How to correctly handle these faults is a difficult problem for electroplating people.
Although the relevant books and magazines list the types of common problems, causes and processing methods, the actual production process will appear in a variety of different situations, and when troubleshooting, it is not easy to "log in" according to the faults listed in the book.
Therefore, when troubleshooting electroplating faults, the fault should be effectively analyzed according to the fault type and the actual situation, which may achieve the "appropriate remedy to the case", and finally correctly deal with and eliminate the fault, and reduce unnecessary losses.
01. Type and causes of electroplating failure:
Electroplating person needs to understand the basic fault type and its causes before the analysis and treatment of electroplating faults.
* The usual electroplating faults are: poor coating binding force, pinhole or burr, brittle, ubiquitous hair, black burning, and poor low current density area.Below, these several faults and their causes are introduced in detail.
① The coating has a poor binding strength.The poor binding force of the coating may be because the surfactant is not clean and still adhered to the surface of the matrix, the oil oxidation film on the matrix metal is not removed, or the concentration of corrosion inhibitor and corrosion removal acid is high.
② The plating has pinholes or burrs.The difference between the pinhole and the burr is: if you wipe the fault with wet paper, the pinhole fault surface is not covered with scraps of paper, and the burr fault surface is stained with scraps of paper.Pinholes are mostly found in copper bright acid and bright nickel plating, common to fine and irregular pinholes (due to oil and organic impurities), conical pinholes (due to hydrogen analysis) and more difficult to identify irregular pinholes (due to small depressions of matrix metal).
③ plating is brittle.The fragility of the coating is mostly due to excessive organic additives or organic impurities in the coating solution.In addition, plating pollution by heavy metal ions or abnormal pH value may also be the cause of fragility.
④ plating pan dot hair flowers.There are the following reasons for the general point: the water quality is bad or the trivalent chromium, blue and white passivation plating after the cleaning is not clean;
* Plating liquid contains more organic matter, such as chloride galvanization;
* The alkaline plating solution remains in the matrix metal pores.The main reason for the hair flower is the poor cleaning of the previous process before plating;
The plating solution is stained with impurities;
Surfactant, surfactant and lumintant.
⑤The plating is burnt and black.Such faults may be because the temperature is not within the process range, the proportion of additives is unbalanced, the current density is too large, the chrome groove current waveform is problematic, and the concentration of the main salt in the plating solution is too low.
⑥The low current density area is not bright.Such failure may be caused by the long use time of the pendant or poor contact, metal impurities in the plating pollution, the current density is not within the process range, the unbalanced proportion of luminant or the quality of luminant problems.
02 、Handling principles and steps of electroplating failure
1. Principle of electroplating failure
① checks whether the process operation conditions and the original and auxiliary materials comply with the process regulations, and insists on handling affairs according to the "chapter".
② should prepare all kinds of materials and background materials in advance, and measures can be taken immediately in case of failure.
③ to the front line to do a careful investigation, "listening is false, seeing is true", to avoid the occurrence of individual personnel to hide the truth, shirk responsibility.
2 Handling steps for plating failure
The first step is to list the various possible situations one by one, carefully analyze them according to the actual performance symptoms, and make a preliminary evaluation of the cause of the failure.
In the second step, the self-trial method verified the various reasons analyzed and estimated by the first step to gradually exclude the non-existing factors.
For example, check equipment and conductive contact (including fittings), water source and environment pollution, harmful impurities in solution, anode, chemical raw materials; small groove test model mainly angle cathode and Hull groove test; job-hopping test in multi-layer electroplating to determine the failure.
The third step is to determine the actual cause of the failure according to the test results, and to conduct further verification.
The fourth step, according to the actual reasons checked, the appropriate medicine to the case, take corresponding measures.
03. Analysis and treatment of electroplating faults
1. Analysis of electroplating failure
Electroplating faults are analyzed, usually from the following four aspects:
① preplating treatment, mainly including electrolytic oil removal, chemical oil removal, polishing, polishing, polishing, pickling, light erosion, weak corrosion, neutralization and other aspects, some factories do not pay attention to cleaning, in order to maintain the concentration of neutralization liquid, must be often tested.
② electroplating process, mainly includes equipment, plating failure, plating composition, cleaning, operation improper, anode, filtration effect, conductive contact, compressed air purification and other aspects.
③ post-plating treatment often causes quality problems due to cleaning, such as the flowing water on the automatic line is not replaced for a long time, resulting in unclean cleaning water. It should be noted that it is best not to stir with air for the last cleaning.
④ environmental pollution, the air often contains some dust, smoke, chemical gases and chemical acid fog.
2. Inspection method for electroplating failure
Inspection method for ① preplating treatment.Carefully check the condition of pre-plating parts.The surface of the coated parts needs to be all wet but not hanging water droplets, nor can there have residual oxidation skin, need to achieve a completely clean state.
Inspection method for the ② equipment.To treat the pendant contact and conductivity seriously, can use the method of small electric beads.
Inspection method of the ③ matrix material.It needs to be carried out in the laboratory, the parts are carefully cleaned with oil and wax remover, and then put them in the newly equipped pretreatment solution, then strict treatment according to the operating conditions, and then put them into the purified plating liquid to further make small tank test plating, and then for identification.
3. Specific method of liquid plating treatment
The following suggestions for common plating problems:
Treatment of the dysregulated ① components.In order to keep the plating liquid composition within the process scope, the plating liquid needs to be analyzed regularly, and to make the plating liquid composition timely adjustment according to the relevant analysis results.
Remove of ② metal impurities: The following methods can be used to solve the problem of metal magazines:
A. Alkalinity precipitation method, for example, for trivalent iron precipitation, the pH value of nickel plating can be adjusted in the liquid.
b. Electrolysis method, if used to remove copper, lead and other impurities in nickel plating solution.
c. Coordination precipitation method, such as nickel plating liquid can be used using QT copper.
The d. Oxidation precipitation method, for example in a nickel plating solution wanting to generate iron hydroxide precipitation, can use hydrogen peroxide to oxidize divalent iron to trivalent iron.
e. Sulfide precipitation method, for example, want to galvanized liquid in the precipitation of copper, lead impurities can use sodium sulfide, potassium sulfide.
③ organic impurities.To solve such problems, you need to be damaged with oxidant, and then adsorb organic matter with activated carbon.
Common oxidants are hydrogen peroxide, potassium permanganate, bisulfite, etc.
It should be noted that whether their by-products should have an impact on the plating.
Removal of the ④ oxidant.When chromium is contained in the nickel plating liquid, it can be reduced with insurance powder.
The specific treatment steps are: first acidify the plating liquid to a pH value of 3 with sulfuric acid, then add the insurance powder 0.02~0.40g/L and stir constantly, the temperature is heated to 60, and the plating liquid pH value is adjusted to 6 after 1h.
Then, it is static for several hours before filtering, to remove the excess insurance powder, the appropriate amount of hydrogen peroxide can be added to the filtered plating solution; finally, the plating solution pH is adjusted to normal with sulfuric acid, and electrolysis plating.
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