Acid zinc and alkaline zinc plating processes help to provide corrosion protection to metal surfaces. Electroplating is a process of coating a metal with a thin layer of another metal using electricity. The metal to be coated is placed in a solution of the metal ions to be deposited, and an electric current is passed through the solution. The metal ions are attracted to the surface of the object and are deposited as a thin layer. Zinc can be plated on metals in different methods.
What is the difference between acid zinc and alkaline zinc plating? In acid zinc plating, the electrolyte solution is acidic, while in alkaline zinc plating, the electrolyte solution is alkaline.
Key Areas Covered
1. What is Acid Zinc Plating
– Definition, Features, Role
2. What is Alkaline Zinc Plating
– Definition, Features, Role
3. Similarities Between Acid Zinc and Alkaline Zinc Plating
– Outline of Common Features
4. Difference Between Acid Zinc and Alkaline Zinc Plating
– Comparison of Key Differences
5. FAQ: Acid Zinc and Alkaline Zinc Plating
– Answers to Frequently Asked Questions
Key Terms
Acid Zinc Plating, Alkaline Zinc Plating
What is Acid Zinc Plating
Acid zinc plating is an electrochemical process that involves depositing a layer of zinc on another metal substrate. Moreover, this process is carried out in an acidic electrolyte solution containing zinc salts, such as zinc sulfate or zinc chloride.
The metal substrate to be plated is first cleaned well using chemicals or using mechanical methods such as blasting. Sometimes pickling is also used to clean the substrate. Here, the metal substrate is immersed in an acidic solution such as sulfuric or hydrochloric acid. The cleaned substrate is then immersed in an acidic zinc plating solution.
An electric current is applied between the substrate (cathode) and a zinc anode. The zinc ions produced at the anode are thus attracted to cathode and they get reduced at the cathode and gets deposited on the metal substrate. This deposition forms a coat on the surface of the metal substrate. After fully plating the metal, it is rinsed to remove the remaining residue if any. Sometimes, the process of passivation is done in oder to increase its corrosion resistance.
Furthermore, factors affecting the quality of plating are electrolyte composition, temperature, current density, substrate preparation and agitation.
Applications of this method are generally in industries like automotive, hardware, electronics, construction and decorations where plating is necessary.
What is Alkaline Zinc Plating
Alkaline zinc plating is a process used to deposit a layer of zinc onto a metal surface. In fact, this method uses an alkaline electrolyte usually containing zinc oxide, sodium hydroxide, and sodium cyanide.
First, the metal to be plated is thoroughly cleaned to remove any dirt or grease. This is done to increase the adhesion of Zn to it. To remove any oil or grease substances, degreasing is also done if necessary. Next, pickling (immersing the metal in an acidic solution) helps to remove any surface oxides. The cleaned metal is then put in a bath containing zinc ions. The next step is the application of an electric current. Zinc ions get deposited on the surface of the metal. Also, rinsing helps to remove any residual chemicals. Then, passivation follows rinsing.
Moreover, applications of alkaline zinc plating are in automotive industry, hardware industry, electronics industry and construction industry.
Similarities Between Acid Zinc and Alkaline Zinc Plating
- Both acid zinc and alkaline zinc plating processes help to provide corrosion protection to metal surfaces.
- Moreover, both methods involve the deposition of a zinc layer onto the metal substrate.
- In addition, they can be applied to a variety of base metals, including steel, iron, copper, and brass.
Difference Between Acid Zinc and Alkaline Zinc Plating
Definition
- Acid zinc plating is an electrochemical process that involves depositing a layer of zinc on another metal substrate. Alkaline zinc plating, on the other hand, is a process used to deposit a layer of zinc onto a metal surface using an alkaline electrolyte.
Solutions
- Acid zinc plating uses acidic solutions, usually containing zinc sulfate or zinc chloride, while alkaline zinc plating uses alkaline solutions, often containing zinc oxide or zinc hydroxide, along with sodium hydroxide or potassium hydroxide.
Temperatures
- Acid zinc plating operates at lower temperatures (around 20-30°C)and requires lower current densities, while alkaline zinc plating operates at higher temperatures (around 40-60°C) and requires higher current densities.
Result
- Acid zinc plating produces a finer-grained, brighter deposit with better ductility and solderability whereas alkaline zinc plating produces a coarser-grained, darker deposit with higher hardness and resistance to abrasion.
Conclusion
Acid zinc plating and alkaline zinc plating are two methods of plating of zinc using electrochemical process. The main difference between acid zinc and alkaline zinc plating is that in acid zinc plating, the electrolyte solution is acidic while in alkaline zinc plating the electrolyte solution is alkaline.
FAQ: Acid Zinc and Alkaline Zinc Plating
1. Is zinc an acid or alkaline?
Zinc is neither an acid nor an alkaline. It is a metal.
2. What pH is good for acid zinc plating?
The ideal pH range for acid zinc plating is between 4.5 and 5.5. In fact, this range guarantees optimal plating efficiency and prevents the formation of undesirable side reactions.
3. What acid removes zinc plating?
Sulfuric acid is a common acid used to remove zinc plating. This is because it reacts with the zinc, forming zinc sulfate and hydrogen gas.
4. What is the principle of zinc plating?
Zinc plating is a process of coating zinc onto a metal surface to protect it from corrosion. Generally, it works by creating a barrier layer that prevents oxygen and moisture from reaching the underlying metal.
5. What chemical is used for zinc plating?
Zinc sulfate is commonly used for zinc plating. It provides zinc ions in solution, which are deposited onto the workpiece during the electrolysis process.
Reference:
1. “Do’s and Don’ts of Acid Zinc Chloride Plating.” Plate World.
2. “Zinc Plating – An Overview.” Science Direct.
Image Courtesy:
1. Image 1: Zinc Chromate Plating
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