1 overview

Modern electroplating cannot be separated from all kinds of additives, but for almost every day to see correct classification and naming of additives, is a question worth to think about. In this paper, the individual lessons learned and seen and heard, some common additives (including additives) to the negative effects of the wrong classification and, expounds some opinions, for the colleague reference and discussion, hope in the field of surface treatment technology can be a good atmosphere of schools of thought contend.

2 bright nickel brightener classification problem

2.1 composition and function of the bright nickel brightener

Bright nickel brightener with respect to its composition can be divided into three categories: primary brightener, secondary brightener and auxiliary brightener. Single and primary brightener can only obtain the crystallization meticulous half light coating, light leveling sex can not meet the requirements. Dominated by saccharin sodium salt, primary brightener [real saccharin (adjacent benzoyl sulfonyl imide) is only slightly soluble in water, 25 ℃ dissolve 1 g to 290 ml water, if use boiling water, you have 25 ml, do not apply]. ALS (allyl sulfonate) is regarded as the auxiliary brightener in the past, but now have higher content of nickel plating brightener, should be regarded as important primary brightener. Primary brightener make the coating produces compressive stress (diastolic stress), make the plating has inflation. Secondary brightener development rapidly, has been applied to the fourth generation in pyridine derivatives were [such as PPS, PPS - OH and propiolic alcohol derivatives (such as diethylamine propiolic amine DEP, propiolic alcohol oxycompound PAP) c] to give priority to. The third generation of BE acetylene (butyl glycol and epoxy chloropropane condensation compound) and its refinement BMP acetylene (butyl glycol c oxycompound) and BEO acetylene (butyl glycol) ethoxy compounds, less dosage, low consumption, is regarded as "long-term brightener, now also in the application. Secondary brightener and primary brightener ratio appropriate, with a quick light efficiency, high leveling. Secondary plating brightener produce tensile stress (shrinkage stress), lead to easy to shrink and peeling of coating. Auxiliary brightener is mainly used to broaden the scope of low Jk area light and its masking copper, such as PS (propargyl sulfonate), ATP (thiourea derivatives) and SSO3 (pyridine hydroxyl propane sulfonate), etc.

As the basic knowledge of using bright nickel brightener, the ratio of the primary and secondary brightener only when appropriate, to minimizes coating internal stress, the bright nickel layer brittleness to minimum. Tensile stress is too large, and prone to brittle peeling of coating, even fall off powder; Compressive stress is too large, coating blister easily, also increased brittleness. Should have a clear understanding. Slightly compressive stress is best, because of the plating slightly inflated, binding force is good. Ratio of the primary and secondary brightener is only appropriate, can in a wide range of Jk realized fast light, high leveling effect.

2.2 divided into brightening agent and softening agent

Now the sale brightener more divided into two categories, brightening agent and softening agent. Softening agent said to come from, is not proven. Brightener components is given priority to with secondary brightener, and softening agent is given priority to with primary brightener and auxiliary brightener, sulfur-containing substance. Disapproved the author thinks that this classification, the reason is: (1) the coating causes of brittle simplified, easy to misleading for will only make the coating brittle tensile stress. To join the primary brightener counteracted compressive stress tensile stress produced by the secondary brightener, coating can be soft and brittle. However, when a glut of softening agent to join, coating compressive stress is too large, the same will be crisp, when adding brightener to offset the large compressive stress, brightener was not softener? (2) the confusion of the cause of the light coating leveling. Theory and practice has proved that only at the beginning, the ratio of the secondary brightener of properly, can realize quick and high light light leveling leveling and wide current density range. Therefore, the primary brightener also plays an important role in light leveling, the synergy effect can not be ignored. Softening agent, in other words, is also a kind of brightener, the same light leveling effect, the function can not completely.

Boric acid in bright nickel liquid and wetting agent of light also makes a significant contribution to the leveling of sex. Experiments found that no wetting agent or its poor quality, high school Jk area coating of gray hair.

Low boric acid and Cl -, Jk area light leveling effect is bad.

2.3 can be divided into the dangers of brightening agent and softening agent

Now, there is theoretical foundation and rich practical experience of production line technology personnel is very lack, make a lot of old electroplating workers deeply worried. Understand technical private boss also is very low, some factory even rely on fertilizer manufacturers of after-sales service.

Adding of electroplating brightener, many people don't even do hull cell test, by feeling or peer to mess with. Bright nickel layer when insufficient light leveling, brightener, to tensile stress caused by peeling coating fall off even pulverization, quick to add softener, results from at least two questions: first, softener, too much coating compressive stress is too large, the same coating brittleness is big, even a small bubble; For sulfur more material in the second, softener, attach or restore after sulfur content increased and the nickel layer passivation, even in the wash water store is a bit long, set of chromium for passivation and deep plating ability more bad, until the white spot, macular, unknown reason again to disorderly adjustable chrome plating liquid. This is the author of common low electroplating factory for brightening agent and softening agent of points in the decorative plating out of trouble, is also the main reason for the unstable product quality. Therefore, the author thought into brightener, brightener, B had better, and how should specify both on the product specification after adding and imbalance fault phenomenon.

The author for a long time since the bright nickel brightener, and work in the first line production, so the conditional through production practice, constantly adjust the formula ratio of brightener inspection, eventually developed an open cylinder and adding the "dual function" of bright nickel brightener, use rise very convenient. As long as the wrong plating solution treatment, proportion of the brightener used for a year or two basic not disorder. So far more than four years after the application, the effect is satisfactory.

3 acid bright copper brightener classification problem

Acid bright copper is undoubtedly the most successful without cyanide copper plating process, application is very wide, even indispensable on plastic electroplating, it is necessary to discuss in detail.

3.1 the complexity of acid copper brightener

Sulfate difficulty of development of bright acid copper plating brightener and use requirement is far higher than bright nickel brightener. Only do Jk plating bright high school easier, but in the long-term production, to ensure that the width of Jk, wide temperature range have complete mirror, little fog and the coating of the color is very difficult. The main reason has the following aspects:

(1) acid copper brightener effect between various components and the content and indispensable synergies between Cl - is very important. Therefore, a good formula proportion is very strict, has the mutual influence between its components, components of each role is difficult to completely.

(2) a lot of component concentration effect, such as M (2 - mercapto benzene and imidazole), N (ethylene thiourea), Cl - (chloride) are within the mg level, a slight change, the performance is reduced.

(3) a lot of raw materials suppliers, but the dosage and performance vary widely. Change a material that needs to adjust the ratio of. Such as different manufacturers provide M or N, some dosage of up to 3 times, the difference between the individual can't even use; P (polyethylene glycol) dosage except related to molecular weight, and closely related to quality, most dependent on imports, substandard products or even make a thin foam coating. Low sulfonated M expanding Jk area light range is less than M; Boil the effects of dissolved directly is better than alkaline help dissolve; Liquor concentration is greater than 0.5 mg/L, easy crystallization precipitation. For a variety of imported dye test results show that some can't use, some makes a deposit of brightener and a half months after deterioration failure.

(4) it is difficult to give attention to both high requirements of the production of a variety of performance indicators. Such as high dye type in 20-28 ℃, low Jk area light coating leveling sex good, suitable for complicated parts, but the maximum permissible liquid temperature is only 32 ℃ or so. Reason of its solution set heating also should be set in refrigeration equipment, general small and medium-sized enterprises do not have this condition, because of the high cost, and is not working.

3.2 the classification of the type of brightener high dye

Imports of acid copper brightener is generally divided into MU (cylinder) and A, B two kinds. But some people will supply A known as the filling agent, agent B called luster agent, this is wrong. Because only adding luster agent and lack of filling agent, light sex is still not good (to mirror effect, good leveling and should be very light); Only addition of filling agent and lack of brightener, Jk area is still difficult to mirror bright, high school and coating used fog, color, especially liquid temperature is lower. Best known as adding agent, adding agent B. In use should determine the best recharge by hull cell test, in order to avoid peer, by feeling confused, lead to low Jk area coating hair dark (using the German original production solution found the fault test, after electrolytic consumption can not diablo, but low Jk area leveling down).

3.3 low, the classification of micro type dye adding agent

Due to high some, such as the best liquid dye narrow temperature range, due to the dye salting out with coagulation and hemp sand inherent defects such as the coating is easy, but to some domestic scholars advocate low Jk type area without dyes with good sex of bright leveling, but is difficult, so far there is no successful process. As the transition, some low, the dye process. This kind of process is necessarily M, N, Sp and P modified form, in which the join area of low and a small amount of high quality dyes.

3.3.1 is divided into two liquid type problems

Acid copper type micro dyes are divided into open type cylinder with the addition of the second liquid goods. Obviously, in adding agent must exist in the proportion of quota of M, N, Sp, P, low area agent and dye. Adding agent only in one, the following problems (years since with practical experience of the system) : M and N under different liquid temperature of consumption rates vary widely. Liquid temperature is high, M consumption rate is greater than N. When the liquid temperature below 15 ℃, consumption rate, even slightly greater than M N. In mass production, it shall timely fine-tuning, summer even need two days time. Test to adjust frequently and with experienced, absolutely use bad M, N, Sp, P system. If only a kind of adding agent, a new liquor may also be better (after all products before the launch of new liquor in the lab to do test, good formula), but the use of a period of time, mass production ratio is bound to cause effect becomes poor, and lack of deep understanding of the system can't self adjusted. A factory in a example is given to illustrate: domestic use this product for a period of time at a big company, a worse effect. The author take fluid under I = 2 a, stir in the hull cell test, the specimens of low-end nearly 2 cm don't see red, bright and side high school Jk area but difficult to reach mirror brightness is fair. With years of experience, first adding M alone, there is a big improvement, and again a small amount of N and under the same conditions, electroplating QuanGuangLiang low area, not only high school Jk area immediately a mirror bright. Visible fault has disorders among liquid: too little M, N, slightly less, Sp and P is enough.

3.3.2 rainfall distribution on 10-12 divided into high and low doses

Some micro type dyestuff acid copper brightener can be divided into high and low doses. The author believes that such a classification there are at least two questions: one, the lack of Sp and P and low light leveling Jk area, and lack of M and N are high, Jk area is still difficult to completely mirror bright; In the second, the low dose if the M and N mixed in certain proportion, inevitable as mentioned two fluid model began to use but in M and N ratio after the effect of variation of the problem.

Incidentally, using low area of material should be careful. The author before the GISS (polyethylene imine alkyl compounds) and AESS) (ethoxy sulfonated fatty amine through contrast test and writing discussed: dosage of GISS AESS only half, but will reduce the coating leveling (the reason is to offset the effect of Sp), the two add too much, coating, especially liquid temperature is high low Jk area prone to fog. The recent "hot carrier" PN (polyethylene imine alkyl salt) after test, found that two things: first, the PN also reduce coating leveling low Jk area; Secondly, in high purity PN in aqueous solution, no matter with acid or alkaline, turbid solution are white. And brightener containing dye must be transferred to acid with sulfuric acid or glacial acetic acid, or dye easy exhalation sink in the brightener (estimates more than basic dye).

So the PN can coexist with dye of agent, remains to be studied.

To sum up, low dyes and the dye type should be divided into open cylinder agent MU, adding agent and adding agent B, and it is best to M and N in A and B respectively, easy to adjust its proportion in the mass production. To develop the acid copper brightener should be combined with production experience, without the pilot laboratory products for a long time, do not easily to the market, or trouble trouble until trouble troubles you.

4 the classification of the sulfate bright tin plating additives

Sulfate bright tin plating brightener is usually divided into a cylinder and adding two (such as SS - 820, the SS - 820). Open cylinder agent containing more divalent tin stabilizer, to weaken the for tetravalent tin oxide become irreversible ivory beta - stannate tendency, but the main light agent content is low; Supplements contains the main light agent and more auxiliary brightener.

Main agent of light for more benzylidene acetone or with a mixture of schiff base class. And the auxiliary brightener is still with formaldehyde. Although some people think that formaldehyde toxic and develop its alternatives, but the effect still not as good as formaldehyde. The author thinks that, electroplating, chemical materials used absolutely harmless to the human body material is very little, but highly toxic, high toxic and low toxicity. Used to think that non-toxic aluminum, food still has strict restrictions; Eating too much Na + but is also harmful to the human body, even the salt should not eat more. If can't use low poison, the plating of this industry should be banned. Don't nervous.

Need to discuss the issues of formaldehyde content in the brightener. Many years the mixed acid tin brightener, author found that liquid temperature below 15 ℃, formaldehyde light effect is obvious; And liquid temperature is high, not only not aggravate degree of coating fog, poor weldability. Therefore, in the mixed brightener without formaldehyde, and then determined by hull cell test should be added and how much. If supplements formaldehyde proportion fixed, the high temperature performance of the brightener will undoubtedly. The author used acid tin, liquid temperature 35 ℃, rather than not fog is very light. How to avoid excessive accumulation of surfactants and the plating is not easy to fog, should not be discussed here.

Therefore, we suggest that supplement can be divided into low and high temperature type two kinds, the former could join which do not add formaldehyde, aid in wide temperature range not achieve fog light deposits.

5. No cyanogen alkaline copper concentrate in the finished product

Someone will import without cyanide alkaline copper concentrate used in plating zinc die casting, began to fair use, after a period of time will produce replacement copper phenomenon, and more and more serious. Where is the problem? The author thinks that: (1) no alkali copper cyanide zinc die casting is higher than plating steel parts requirements. Potential to be more negative than iron, of zinc and copper in the potential difference is bigger, so are more likely to produce replacement copper. Test in the process of copper on steel parts do not produce displacement, in zinc die-casting parts or galvanized parts replacement copper. Therefore, must be used for Cu2 + has a strong coordination ability of the composite chelating agent, so as to reduce the activity of Cu2 + was very low, but it also causes less Jk. Although adding suitable amount of potassium nitrate can expand Jk, but because of NO3 - would promote steel passivation and not conducive to hydrogen evolution electrolytic activation, and affect the adhesion strength of the steel parts no alkali cyanide copper plating, so the two materials should be different plating technology (zinc iron easy passivation). (2) due to concentrate for simple, therefore with the increase of time, will keep out of the loss, chelating agent and Cu2 + can be added by anodic dissolution. Therefore, even if adding concentrate, mixture ratio will decrease continuously, the displacement of copper occur eventually. Of course, low pH, coordination ability is weak, will also be a problem.

No alkali cyanide copper concentrate as commodity, therefore, not only made a, also should have at least a chelating agent containing only and does not contain Cu2 + and adding agent can adjust pH. When plating solution deep plating ability poor or replacement copper surface slightly, test of adding, mixture ratio in allowed range fluctuations. Otherwise, even if is electroplating process for steel parts, sooner or later will also be a problem.

6. Conclusion

Many other additives also problems of categorization, go here. For electroplating additives shall be correct classification and naming, when indicated.