Click here to get more.
Thread starter
meganw
Start date
Apr 7,Tags
In summary: Therefore, the piece of metal inserted into the solution should be the cathode, and in this case, zinc would be the best choice according to the standard reduction potentials chart. In summary, to plate out nickel from a nickel (II) nitrate solution, you should use zinc as the cathode.
meganw
"Plating" Metal - Cathode or Anode?
Science Advisor
Gold Member
Further down on the list reduces further up on the list. So zinc will work well, and copper not so much.There are a few mnemonics to help with remembering electrochemistry. In this case, we have &#;An Ox Red Cat,&#; or oxidation occurs at the anode while reduction occurs at the cathode. So the Niis reduced to nickel metal (plated) at the cathode.
Plating metal is a process in which a thin layer of one metal is deposited onto the surface of another metal. It is used for a variety of reasons, including improving the appearance of the metal, increasing its resistance to corrosion, and enhancing its electrical conductivity.
In plating metal, the cathode is the metal object being plated, and the anode is the source of the plating material. The anode is connected to the positive terminal of a power supply, while the cathode is connected to the negative terminal. This causes the plating material to be attracted to the cathode and deposited onto its surface.
The metal that is more reactive or more easily oxidized should be the anode, while the less reactive or less easily oxidized metal should be the cathode. This ensures that the anode will provide a source of positive ions for plating, while the cathode will attract and receive those ions.
No, not all metals can be used as a cathode or anode in plating. The metal must have good electrical conductivity and must not react with the plating material. Commonly used cathode metals include copper, nickel, and silver, while commonly used anode metals include zinc, tin, and chromium.
The quality of the plating metal process can be affected by factors such as the purity and composition of the plating material, the current and voltage used, the temperature and pH of the plating solution, and the cleanliness and preparation of the cathode surface. Proper control of these variables is necessary to achieve a desired plating result.
Anode in the plating of the Applied Research
1&#;Introduction
Electroplating has experienced 100 years of development, has been from a craft into a science, has become the subject of metal corrosion and protection of an important branch of plating in order to process simple equipment and operation easier, the advantages of low cost have become a wide range of surface treatment technologies in a common technique.
Electroplating is a metal substrate surface decoration, protection, and access to some of the new performance of a process approach is a multidisciplinary integrated technologies. The beginning of the new century, technology and market competition on the plating process and products have become increasingly demanding high plating quality of the product, the output and efficiency of a direct impact on the competitiveness of a number of enterprise products. Therefore, surface treatment, including electroplating technology is advancing with the times, innovative, high-quality, low-cost, non-polluting, low-cost, multi-color, decorative, functional and automated high new era.
2&#;Anode effects
In electroplating, the process and anodic process is a pair of interdependent contradictory. It is true that the process of the main aspects of contradictory research work more, but the anodic process is often due to lack of sufficient attention to failures caused by electroplating.
Litian Century contains other products and information you need, so please check it out.
2.1 soluble Anode and the choice of insoluble anode
2.1.1 soluble anode
In electroplating, there are soluble and insoluble anode divided, in most plating bath species and the use of soluble anodes, their reasons are:
(1) Coating of metal ion concentration is easy to control: deposition of metal ions can be added by anodic dissolution, and the anodic dissolution current efficiency is often greater than the cathode current efficiency of metal deposition, coupled with plating bath out of the loss, in order to ensure of the main salt stability.
(2) Relatively stable bath composition: If using an insoluble anode, the anodic oxygen evolution or make bath-component electrochemical oxidation or chemical oxidation. For example: in the oxide bath, the oxide is oxidized into carbonate and ammonia, which will make bath salts component instability or due to the accumulation of carbon coating would rough, using soluble anode, as long as take measures to prevent anode, The oxidation reaction does not occur.
(3) The plating bath pH, relatively stable, such as the use of insoluble anodes, due to OH-discharge anode and cathode discharge of H + discharge efficiency of the different, leading to acidification of bath.
(4) Plating maintenance costs low, the general use coating metal cheaper than the use of their salts, and simple operation, but to add salt so as to enhance operation of the trouble, but also tend to increase the volume of bath.
2.1.2 Selection of insoluble anode
For these reasons, the general use of soluble anodes, but some kinds of plating using insoluble anodes also. For example:
(1) Hexavalent chromium plating process: As the chromium mainly dissolved in the form of trivalent chromium bath components can not be so stable, so use of tin-lead or lead-antimony-insoluble anode.
(2) zincate: As the self-dissolution in an alkaline solution is very significant, and thus the efficiency of the anode is greater than the cathode efficiency of zinc plating bath components accumulated disorders, it is lack of use of insoluble and soluble anode zinc anode mix, so that the control of the metal ions increased again to ensure uniform distribution of the power line. 2.2 The ideal of soluble and insoluble anode should have the conditions for
2.2.1 soluble anode
(1) Dissolution performance, limiting current density higher.
(2) The anode and cathode current efficiency should be as close as possible.
(3) Dissolved evenly as far as possible to avoid anode mud.
(4) Should be sufficient purity to avoid contamination of soluble impurities, degradation bath Coating.
2.2.2 Insoluble Anodes
Should have good conductivity and high chemical and electrochemical stability.
2.3 soluble and insoluble anode transformation
The soluble and insoluble anode anode under certain conditions, the mutual transformation, we must master the soluble anode and the insoluble anode bath in different characteristics. Generally speaking, soluble anode and the insoluble anode in electroplating, in common with the cathode and the bath group of electrolytic cell, the conduction current in oxidation reaction, differences, the former plating process, has also produced chemical and electrochemical dissolution of metal ions, while the latter is not the existence of metal dissolution. The role of the former is based on complementary metal cathode deposition dissolution; make bath composition remained stable. Such as the soluble dissolved too fast, too slow or passive, solution stability of the damage would have been a failure, how to prevent these problems, we must understand the insoluble anode, in addition to conduction current and the oxidation reaction or oxygen evolution, we must also note that its process special needs.
Adjust the two different anode, we must also tend to note the different commonly used insoluble anode iron, nickel, lead, iron and aluminum, stainless steel and other characteristics of different metals. A number of failures and losses from the abuse caused by the insoluble anode, because soluble and insoluble is a relative term, if the metal is soluble in a certain bath anode, but in another solution, it became insoluble anode. As of lead in the chrome plating is insoluble anode, but the lead is soluble in the plating anode. Pairs of stainless steel, because it contains chromium in the nickel plating is not as insoluble anodes, or chromium pollution, there will be failure, exclusion is difficult, but it does not exist in an alkaline solution of this soluble, can be used for insoluble anode. Some of metal in different bath, although can be used as the soluble anode, but with the current density increased, dissolved oxygen precipitation stops, but also to become insoluble anode. Sometimes, some bath (such as alkaline tin plating) and the anode have to be in a semi-passive state. Otherwise, some of tin anode in order to Sn2 + ions dissolved Er Shi hair gray and rough coating. Therefore, the application should be adept at grasping the role of these different metals, features, service shall be understood in theory, the application is reasonable, and take effective application of technical measures.
3&#;Anode in electroplating applications, several practical problems
3.1 Anode Material
In practice, the anode should be selected with high purity (rolling anode), has both increased anodic current density, but also to achieve the uniformity of anodic dissolution, reducing production of anode mud sediment, making it difficult for the anode passivation.
3.2 The shape of the anode
Designed to hang with, they should make a major surface-plated pieces with the face of the anode and in parallel in different parts of the cathode and anode to narrow the distance between the ratio, if necessary, use of pictographic anode (mainly for chrome) and the auxiliary anode (for deep - Hole or tubular plating), so as to ensure uniform distribution of power lines, so that the capacity to improve the dispersion bath.
3.3 The anodic and cathodic distance
Within a certain range, increasing the distance between the cathode and the anode can improve the dispersion capacity, In addition, also make away, near the cathode and the anode distance ratio (L12=K) decreased the initial current distribution will be improved to enhance dispersion capacity. But not unlimited increase the very pitch, otherwise, the plating tank width and area increased, while cell voltage rise, energy-large.
3.4 The anodic and area
General plating kinds of anode area should be larger than the cathode, usually 2:1, a small number of 1:1, the individual as the acid copper plating for 3 ~ 4:1. A special case: Practice has proved that this is to prevent anode passivation, to ensure the normal anodic dissolution and increasing the current density plating bath effective measures.
3.5 soluble and insoluble anode area ratio
This is to ensure the normal anodic dissolution, maintaining a stable plating bath composition and effective measures, such as: alkaline zinc plating bath soluble and insoluble anode area should be 3:1; Also, because electroplating fluid mixing anode generally selected anode baskets, anode bags, the baskets, bags are generally insoluble anode, the application should pay attention to this aspect.
3.6 We must be good to master a set of methods to prevent anode passivation.
(1) Master the anodic and area ratio and current density, control norms in the process of production. Practice has proved that this is to prevent anode passivation, to ensure the normal anodic dissolution of effective measures. In addition to alkaline tin plating of the cathode area should be larger than the anode (1.5 ~ 2.5:1), the general plating species should be larger than the cathode-anode area, usually 2:1, a small number of 1:1, the individual as the acid copper plating 3 ~ 4:1, in order and process specifications anodic and cathodic current density correspond to the general Dk> DA in order to make anodic dissolution and prevention of the normal passivation. As noted above, any increase the anodic current density or by hanging plating (cathode) without a corresponding increase and adjust the anode area, can be caused by anode passivation.
(2) Analysis of the anode passivation. How Analysis of anode passivation took place can be a sudden increase of voltage from the rectifier detected. By plating tank supply current show, in addition to current meter, as well as voltage meter to indicate cell voltage, cell voltage, including cathode potential k, anodic potential umbrella a, trough IR drop within and outside the tank outside the IR voltage drop, ie E = This four-part will affect the current density, due to differences in the specific conditions of different plating tank of cell voltage is also different. But at the same tank, such as a sudden increase in cell voltage indicates that the plating is not normal. According to Ohm's law, when the circuit resistance increases, is not conductive rod being exposed, parts, it can assert that the anode passivation, the voltage increases, usually in order to monitor the plating. How to identify the passivation of the anode plate situation? As zinc anodic dissolution of zinc plates are gray-black, and white (zinc oxide), or passivation; acid copper plating when the passive film is black hair gray, indicating that the crystallization CuSO4, Removed Automatic fall, some completely non-black film; cyanide soluble copper-tin alloy plating normally a "fish scale" pattern, after passivation black; nickel anode dissolution of the normal gray, reddish-brown after passivation passivation film.
(3) Temperature effects on the formation of anode passivation. A variety of processes have different temperature requirements, tank temperature is too high, too low for its dissolution and passivation have a direct impact is in the copper at room temperature 5 ~ 40 &#;, higher than the ceiling, light disappeared, Yang easily passivated. Cyanide copper-nickel alloy in 60 ~ 65 &#; carried out under high anodic dissolution fast, cyanide decomposition increased, easy-to copper-tin ratio and low anodic polarization increased passivation. Is often easy to mistakenly believe that under all circumstances, raising the temperature can accelerate the anodic dissolution, which must meet the plating species to another. Of course, a general warming may increase the solubility of salts to improve the anodic dissolution performance, increase conductivity, but the temperature is too low and because the value of the critical passivation current density smaller than that at high temperatures, the anode is also easy to passivation. All this must be flexible.
(4), good selection of high purity of the anode and attention to the changing technological factors, to prevent anode passivation. Anode casting and rolling are usually two kinds, the former despite the economic, but a lot of impurities and insoluble sediment will shorten the purification period.
4&#;Anode in electroplating production role
4.1 The role of anode
Comprehensive above, the role of the anode in the following areas:
(1) The cathode, electrolyte electrolytic cell composed of closed-loop, the conduction current and to oxidation.
(2) The chemical and electrochemical dissolution of metal ions produced to supplement the cathodic deposition of metal ions.
(3) To enable the bath composition remained stable.
(4) A change in the anode process parameters to improve the power-line distribution, the bath of the dispersion capacity, and reduce the plating production costs.
4.2 production instance
Here are three examples (one cases of failure, the economic costs of two cases)
(1) in alkaline zincate zinc plating is thin, partial plating is not on the black coating failure: In the past, my college classmate zincate zinc plating line, the normal production after the initial production, product quality is also good However, products will soon appear black, and some are not on the plated part, after testing, the high zinc content, so reduce the zinc plate, by hanging iron. This increased to minus, resulting in excessive iron anode (more than 2 / 3 basically reached 1:1), and then will be in a slot (2t Bath) plus NaOH75Kg. Failure can not be ruled out, but also flavored blue Su 1Kg and DE and EDTA5Kg, and problems become more serious, and finally ck778 reprocessed rationalize anode, was back to normal.
Cause similar failures due to lack of anode applied technology, ignoring the scientific maintenance management practices. If the plant first to discover that the adjustment of the high zinc anode, but the increase or decrease in the number of the lack of "quantity" concept, the general said alkaline zincate zinc plating bath, the soluble and insoluble anode area should be 3:1 is appropriate. Each slot in the anode of the plant 2 / 3 is iron, zinc plate with iron hanging baskets around 1:5 between the total area and this will inevitably result in the low zinc content, although zinc electrolyte to the dispersion of small abilities have improved, but allows the use of the current density is significantly reduced accordingly, so that can only reduce the current density in order to be qualified in the coatings, but with lower current density the deposition rate of zinc was experiencing decline, there will be a thin coating and partial plating not be reached. In addition, from a theoretical analysis of iron in alkaline zincate zinc plating, basically does not dissolve, but it ignores the pre-treatment cleaning is not the net result of the chlorine into chloride ions and additives in the decomposition of propane being the chloride ion, can make iron-activated and dissolved Fe2 + and other impurities out of pollution (Cu2 +, Pb2 + trace), resulting in black plating, while Fe2 + ions and other impurities into the passive film coating layer also caused discoloration. Cra ham so that, in alkaline zincate zinc plating solution, such as zinc and iron insoluble anode anode and used, it should be noted that with the changes in current density, iron may not achieve the role of the insoluble anode, while stopping plating because of a zinc and iron increased the contact corrosion of zinc to leach out; the zinc anode into iron basket when used similar phenomenon also occur.
5&#;Conclusion
In short, the metal anodic oxidation process is much more complex than the cathodic reduction process, worthy of serious study, but the production, such as the above is often neglected and rarely fails to analyze. If, as the same attention to Bath to maintain the anode could be avoided by a lot of failures and losses. According to different process requirements, the use of anode properties to stabilize the craft, apparently to improve plating quality and reduce the cost effective way.
Are you interested in learning more about Plating Anode? Contact us today to secure an expert consultation!