- July 26, 2024
Electroplating and anodizing help to improve the quality of metal surfaces during finishing. They are the two common finishing processes that enhance corrosion resistance, durability, and surface appearance. Thus, to adopt the best applications of these processes, one has to understand the differences and similarities between the two.
This article discusses the comparison between electroplating and anodizing. It highlights the different processes involved in the two techniques, their benefits and disadvantages, and various types.
What are the Differences Between Electroplating and Anodizing?
The main difference between these two techniques is in their processes. However, the principle of electroplating has to do with coating a metal surface with another metal compound, while anodizing entails thickening the natural oxide on a metal surface. Here are the differences in electroplating vs. anodizing.
Processing Methods
The metal to be electroplated is called the substrate and is connected to the cathode in electroplating. The electrolyte, which contains metal ions for electroplating, is the solution. A direct current passes through the solution to dissolve metal ions from the anode and deposit them on the substrate. Two distinct materials are involved: the material to be plated and the plating material. For example, in a plating process involving beryllium copper and nickel, the plating layer is nickel, and the substrate is beryllium copper.
Anodization is the process of treating metal with electrochemicals to produce a thin film coating on its surface. A thin coating forms on the surface of the treated material, which acts as the anode, when electricity is applied in the electrolyte. If the aluminum alloy oxidizes, an aluminum oxide layer will form on the surface of the workpiece. Alumina is characterized by its chemical stability, resistance to oxidation and acid corrosion, and capacity to dye colors.
Coating Objects
The majority of plated items are metal. The most commonly used plating metals are nickel, chromium, tin, copper, silver, and gold. This technique is commonly used for platings such as gold, chrome, nickel, etc. Anodizing is a metal surface treatment method that thickens the natural oxide layer on the metal. The metals, aluminum, and titanium, commonly used are anodized with the right electrolyte.
Working Principles
During processing in anodizing, the anode is the substance on which the process is carried out. However, in electroplating, the cathode is the substance used for coating, mostly a metal. The metal anode ions deposit their electrons on the cathode due to the charge effect of an electroplating process. The ions are replenished immediately following the dissolution of the anode metal. The anodizing process is primarily used for aluminum surfaces due to their high reactivity, which readily forms a durable oxide layer.
Weight Result
Anodizing adds a lightweight layer of about 0.0001 – 0.001 inches to the surface of the aluminum material which normally increases the weight by a negligible 1% or less. However, electroplating leaves the product heavier as it deposits about 0.005 inches of thickness which may contribute to an additional 10% weight on the metal.
Strength
Electroplating can improve the tensile strength of the metal material used by the constant depositing of other metals on the surface. depending on the plated material and thickness, electroplating can increase the tensile strength of a metal by up to 20%. Anodizing on the other hand increases many other surface qualities like hardness and rust resistance but does not really improve the strength of a metal.
What is Anodizing?
Anodizing is an electrochemical procedure that gives a metallic surface an anodic oxide finish. Aluminum is the most suitable metal for anodizing, though other nonferrous metals like titanium and magnesium can also be treated in this way. The aluminum substrate provides the entire aluminum oxide that makes up the anodic oxide structure.
This aluminum anodizing resists chipping and peeling because it is completely merged with the underlying metal substrate instead of being applied topically like paint or plating. Its well-organized porosity structure also makes subsequent processes like painting and sealing possible.
Purpose of Anodizing
The anodizing process enhances the durability, strength, and appearance of a metallic material surface. The process works by thickening the natural oxide layer, which helps to hinder corrosion and wear on the metal. It also aids in the improvement of adhesion for paint and glues, which are very important in metal finishing.
Anodizing metals give them some cosmetic effects like preventing galling in threaded parts as well as colorization. It also helps to protect the surface of the metals from degradation by increasing hardness and thickness. Industries like construction, aerospace, and automotive use anodizing to enhance the overall performance, aesthetics, and longevity of metal components.
How Does Anodizing Work?
During anodizing, aluminum alloys are most used because they oxidize easily, aiding the regulation of oxide layer development on them.
First, the metal is pre-treated through cleaning and etching to remove impurities. If necessary, the metal undergoes electrolytic coloring to deposit colored ions in the pores of the metal, an optional step in the process. The metal (anode) is then passed through an electric current to oxidize the surface.
When the current passes, the metal surface reacts with oxygen ions in the solution which forms an oxide layer on the metal Al2O3 or TiO2). The layers continue to develop as more ions are deposited leading to more thickness. After this, porosity increases to allow dye and other substances to be deposited.
The final stage of anodizing is the sealing of the pores with hot water to get a durable, non-porous finish. This provides a non-conductive, anodized object resistant to wear and corrosion.
Types of Anodizing Process
Here is a breakdown of the types of anodizing:
1. Chromic Acid Anodization
With an oxide layer thickness of 0.00002 to 0.0001 inches, chromic acid anodizing (Type I) is the thinnest surface of the three main anodizing techniques. Aluminum can withstand corrosion just as well when sealed properly, thanks to the oxide layer created by chromic acid anodization.
Type I oxide coatings have a grayish hue and absorb less color when dyed because the coating layer is thinner. The application of chromic acid anodizing as a decorative finish is limited by this grayish cast.
Among the main advantages of chromic acid anodizing are its electrically non-conductive qualities and strong adhesive attachment to other items. Chromic acid anodizing is commonly applied to welded components and aeronautical parts and as a base for further painting.
2. Anodizing with Sulfuric Acid
The most often used anodizing technique is Type II, or sulfuric acid. The sulfuric acid anodizing process results in films that are between 0.0002 and 0.001 inches thick. The part’s surface is altered by the oxide buildup, which makes it ideal for circumstances where abrasion resistance and hardness are required.
Using the porosity of sulfuric acid coatings before sealing allows for a colorful surface finishing on aluminum and related alloys. Dyes are easily absorbed by the permeable aluminum oxide. When the dye has been applied, sealing the anodic oxide film helps prevent color fading while the part is in use. With this anodizing method, you can choose from a variety of colors, such as red, black, gray, and brown.
Sulfuric acid anodizing is less expensive and takes less time to achieve the appropriate thickness than other anodizing techniques. Type II anodizing is frequently used on optical and electronic components, hydraulic valve bodies, and computer and electronics enclosures.
3. Hard Coat or Hard Anodize
The usual method for applying hard coat anodizing is with an electrolyte based on sulfuric acid. Compared to sulfuric acid anodizing, it yields an oxide coating that is noticeably thicker and denser.
Hard anodizing typically has a coating thickness of 0.0005 to 0.002 inches. For applications needing excellent abrasion resistance in corrosive conditions, the harsh anodizing procedure is advised. In situations where improved electrical insulation is required, it may also be helpful.
Type III anodized coatings help remanufacture out-of-spec components or refurbish worn coatings since they can become thicker with multiple depositions of oxide layers.
Types of Metals Suitable for Anodizing
Although aluminum and aluminum alloys are the most often anodized materials, other metals like titanium, manganese, magnesium, zinc, and stainless steel can also be anodized. The surface of anodized aluminum becomes three times more durable than that of ordinary aluminum and remains unbreakable even after coloring.
Benefits of Anodizing
- Protects the product from corrosion: the extra layer of substance formed by anodizing helps to inhibit rust and corrosion on metals, thereby elongating their lifespan.
- Enhances durability: anodizing makes the surface of the metal more resistant to wear, which improves the durability of the object.
- Enhances the appearance: the surface of an anodized metal becomes more suitable for dyeing and painting, as the process transforms the chemical makeup of the metal.
Limitations of Anodizing
- Visible touch-up: colored coatings done through anodizing are prone to scratching. the touch on these scratches is visible.
- Limited color selection: the chemicals used in the anodizing process severely limit the color range an anodized metal has. Thus, the color options are reduced drastically, leaving the metal with limited choices for painting or dyeing.
Common Applications of Anodized Products
Anodizing improves the aesthetics of the product or object, and this effect, together with its durability, gives the process the ability to influence many industries.
Construction Industry
In the construction space, anodized products like aluminum trellises, railing systems, and barbecue canopies are used. The anodized finish gives the build an elongated lifespan because aluminum rusts when coated. Also, anodized products do not show wear under UV and saltwater exposure.
Aerospace Industry
In aerospace, aluminum extrusions like trusses come with aluminum finishes to avoid rust or degradation of the material. The anodized finish of trusses offers far superior optical and thermal control.
Medical Industry
Anodizing helps in manufacturing medical devices used in the field of medicine for different purposes. for example, medical devices like joint replacements and surgical instruments are mostly anodized products.
Automotive Industry
In the automotive sector anodizing is used to enhance corrosion resistance on engine blocks and wheels. it also enhances the aesthetics of exterior trims, handles, and grills giving them an attractive finish.
What is Electroplating?
Electroplating is an electrochemical process where a plating layer of metal is deposited on another metal called the substrate. This process can enhance the aesthetic appeal, appearance, conductivity, and corrosion resistance of the substrate. Metals that can be used for electroplating include nickel, gold, silver, copper, chromium, and zinc.
Besides, electroplating metals also help to improve the functionality of the substrate and commonly used in the aerospace, automotive, and jewelry industries. It can be used to improve the acceptance rate of a metal for other protective coatings to prevent rust and wear.
Purpose of Electroplating
Electroplating is used to add a thin layer of metal to a conductive surface to improve its conductivity, corrosion resistance, durability, or look. In sectors such as the automotive, electronics, and jewelry manufacturing industries, this can be required to satisfy certain functional or aesthetic standards.
The process of electroplating can also improve the physical features of a metal. It offers corrosion resistance, allowing metal components used in a variety of sectors to last longer. Electroplating is ideal for electrical and electronic applications because it increases conductivity. It also boasts a lovely finish that amplifies the visual attractiveness of items like jewelry and car trim.
How Does Electroplating Work?
During the electrochemical process of electroplating, an electrolytic cell deposits an ionic metal coating on a conducting surface. The metal object on which the deposition is made, or substrate, undergoes a prior cleaning phase before it is submerged in an electrolytic solution.
Then, direct current is added to the solution, where the substrate is connected to the cathode and the plating material is connected to the anode. Metal ions dissolve from the anode into the solution as the current flows and deposits on the metal connected to the cathode.
Thus, the metal has an even but thin layer of the plating material. Electrolyte composition, density, and plating time can be regulated to influence the thickness of the layer.
Types of Electroplating Techniques
Electroplating has different types, with each one adapting to a specific application and material. Here are the types of electroplating:
Nickel Plating
This type of plating can serve as underlying plating for chromium, as it bonds with aluminum and copper frequently. During the electroless nickel plating process, an alloy of nickel and phosphorus is used, it easily improves hardness and corrosion resistance. It comes in handy in various industries like automotive, aerospace, and electronics for both decorative and functional reasons.
Chromium Plating
In this plating type, chromium is applied to another of metal part surface to improve its appearance. Due to its ability to restore tolerances on damaged parts and give a shiny finish, chromium plating is mostly used in the automotive industry for attractive car components.
Copper Plating
This involves the use of copper as a coating material to electroplate metal objects. It is the best pretreatment coating for other metal plating and is used widely on metals for electronic components. Copper plating is suitable for electronic components, printed circuit boards, and electrical industries.
Gold Plating
Gold plating involves the deposition of a thin layer of gold on another metal part surface. It comes in handy in jewelry production, electronics, and decorative industries.
Different Metals Suitable for Electroplating
Metals used in electroplating processes depend on the application and material finish required. Some of the popular ones are zinc, gold, copper, nickel, chromium, cadmium, silver, zinc, and brass. Each metal has its unique properties and features it brings to the finished product.
For example, Zinc is a cheaper option that helps to prevent corrosion in iron and steel materials. Chromium used in plating gives the substrate a glossy finish while maintaining an anti-corrosive feature.
Benefits of Electroplating
- Electroplating places a substrate on a metal surface which provides a protective coating against wear or corrosion;
- It improves the functionality of a metal or material and also increases its lifespan;
- The plating process can enhance the electrical conductivity of a metal material;
- Metallic elements combine during electroplating to improve decorative finishes on metal objects, enhancing their appearance or appeal.
Limitations of Electroplating
- The process of electroplating is expensive as you’ll need several metal elements, reagents, and other costly components;
- Covering the metal surfaces with other metal layers and components consumes time and makes the process slow and lengthy;
- the process generates hazardous substances into the environment causing pollution.
Similarities between Electroplating and Anodizing
While there are numerous differences between the two metal coating processes, there exist some similarities. One of the obvious similarities is that they are both electrochemical processes that use chemical substrates. Moreover, since they are coating techniques, there is a deposition of a substance on the surface of a metal in both anodized and electroplating.
In both processes, there is the presence of an anode and cathode in an electrolytic solution. At the same time, these processes are used to enhance the appearance and functionality of metal objects. While Electroplating deposits metals and anodizing, oxidative layers, the two procedures increase resistance to wear, corrosion, and damage.
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Conclusion
The concept between anodizing vs plating will always depend on the material in question and the application of the end product. Both metal coating techniques have their strengths and weaknesses; it all comes down to specific requirements and preferences. Moreover, when comparing the two techniques, the nature of the subject metal should be prioritized.
FAQs
Which is more durable: anodized or electroplated surfaces?
Anodized surfaces are inherently more resistant to corrosion due to their protective oxide layer. Electroplated surfaces are more wear-resistant.
What maintenance is best for anodized and electroplated surfaces?
The best maintenance tip for electroplated and anodized surfaces is to clean them with soap and water to remove dirt, then clean them with a soft microfiber cloth afterward.
