The technique of electroplating involves coating one metal on another metal surface, whereas anodizing involves thickening the naturally occurring oxide layer on the surface of the metal surfaces. This is the main distinction between the two processes.

The object of interest serves as the cathode of an electrochemical cell during the electroplating process, but during the anodizing process, the object serves as the anode, hence the name anodizing.

In this article, we will look at what anodizing and plating are, their benefits, advantages, key similarities, and differences between the two techniques

 

What Is Anodizing?

Anodizing is an electrochemical process that converts the metal surface into a decorative, durable, corrosion-resistant, anodic oxide finish. Although other nonferrous metals, such as magnesium and titanium, can also be anodized, aluminum is best suited for the process. The anodic oxide structure, made completely of aluminum oxide, comes from the aluminum substrate. 

This aluminum oxide is totally integrated with the underlying metal substrate rather than being applied to the surface like paint or plating, making it resistant to chipping and peeling. In addition, its well-organized porous structure enables further procedures like coloring and sealing. Aluminum is anodized by dipping it into an acid electrolyte bath and then running an electric current through it. 

The anodizing tank has a cathode mounted inside of it; aluminum serves as the anode, causing oxygen ions to be released from the electrolyte and combined with aluminum atoms on the surface of the component being anodized. Therefore, anodizing is the enhancement of a naturally occurring phenomenon through carefully controlled oxidation.

 

what is anodizing

Benefits Of Anodizing

The benefits of anodizing are included below with: 

Durability

The majority of anodized items have extraordinarily long lifespans and provide significant financial benefits due to maintenance and operational cost savings. For complete bonding and unrivaled adhesion, anodizing is a reactive finish that is merged with the underlying metal.

Color Retention

The majority of anodized items have extraordinarily long lifespans and provide significant financial benefits due to maintenance and operational cost savings. For complete bonding and unrivaled adhesion, anodizing is a reactive finish that is merged with the underlying metal.

Simple Maintenance

There are hardly any scars or wear from fabrication, handling, installation, routine surface dirt cleaning, or use. An anodized surface may typically be cleaned with mild soap and water or rinsed to bring back its original appearance. For harder deposits, you can use mild abrasive cleansers.

Aesthetics

Anodizing decreases or completely removes color inconsistencies while providing a vast array of gloss and color options. In addition, Anodizing, unlike other finishes, enables aluminum to keep its metallic appearance.

Cost

Greater long-term value is produced by a lower initial finishing cost combined with lower maintenance expenditures.

Safety and Health

Anodizing is a harmless technique that has no negative effects on health. Anodized finishes are non-toxic, stable chemically, won’t break down, and can withstand heat up to the melting point of aluminum (1,221 degrees F.)

The anodizing process is non-hazardous and has no toxic or dangerous byproducts because it strengthens a naturally existing oxide reaction.

 

Anodizing benefits

Disadvantages Of Anodizing Aluminium

The disadvantages of anodizing aluminum include: 

  • Only certain grades of aluminum are suitable for this technique,
  • Stainless steel, which is resistant to mortar, salt, chlorine, and marine environments, cannot be utilized with this product.
  • This process draws from the base metal, allowing for color changes.
  • In low-grade metals, no match is achievable across batches, making consistency between batches more difficult to recreate than in high-grade metals, where a 95% match is possible.
  • The priciest option for modest quantities (requires a higher-grade alloy in addition to the already high set-up costs).

 

Types Of Anodizing

 

Type 1 – Anodizing

 

Type 1 – Anodizing

Commonly known as chromic acid anodizing, it is a popular method that coats the metal substrate with an oxide layer.

Chromic acid anodizing, the thinnest of the three primary anodic coating methods, produces an electrically non-conductive surface with enhanced scratch and corrosion resistance.

Type 1 is the preferred procedure for aerospace and other industrial components that may bend due to heat changes or mechanical means since the resulting oxide layer is thin.

 

sulfuric acid anodize

 

Type II – Sulfuric Acid Anodize

The most used anodizing technique is type 2 anodizing, often known as sulfuric acid anodize. A protective coating of aluminum oxide is created by altering the surface of an aluminum substrate material.

It is best suited for situations where hardness and abrasion resistance are necessary.

Additionally, sulfuric acid anodize can be used as a foundation for paint systems or to increase surface corrosion and protection under demanding operating circumstances. In particular, the fabrication of colorful surface finishes on aluminum, and related alloys take advantage of the porous character of sulfuric acid coatings before sealing.

 

Hardcoat Anodize

 

Type III – Hardcoat Anodize

Type III aluminum anodizing, also known as hard coat anodizing or hard anodizing, is used to improve the thermal and dialectical properties of treated aluminum products and their wear and corrosion resistance. In addition, with Type III anodizing, the capacity to retain lubricants and PTFE coatings (such as Sanford HardlubeTM) also improves.

The thickness of the naturally existing oxide layer on aluminum surfaces is increased through hard coat anodizing. With Type III anodizing, natural oxide layers’ thickness, typically 2 to 3 nanometers, can be raised to or even above 50 m* (0.002″). A very regular, uniform layer is produced across the whole surface of the treated object by properly placed hard anodic coatings.

The military standard Mil-A-8625 Type III category gave rise to the abbreviation Type III anodizing. * μm = micrometer (1000x the length of a nanometer).

 

Chemical Film / Alodine

To achieve outcomes similar to anodization, this process involves coating the component with alodine.

When the anodizing aluminum method was created in the early 1900s, producers utilized chromic acid frequently, but today the majority of parts are anodized with sulfuric acid (Type II and Type III).

There are numerous options for adding color when anodizing aluminum components. In order to color the portion, a pigment is injected into its open pores. To maintain the desired hue, the colored pigment is sealed off as it reaches the surface. This preserves the appearance of your parts by producing a visual effect that won’t wear out or be scraped off.

 

What Is Plating?

Plating is a surface covering in which a metal is deposited on a conductive surface. The electroplate is used for corrosion inhibition, improved solderability, to harden, improved wearability, reduced friction, improved paint adhesion, altered conductivity, or for radiation shielding.

 

Benefits Of Plating

The benefits of plating include: 

 

Resistance To Heat

Metal plating increases the heat resistance of products, particularly when using a silver-plating process, which has a very high heat threshold. Due to this benefit, metal finishing is a preferred option in the aviation and automobile industries, where exposure to high temperatures is inevitable.

 

Increased Durability

Metal finishing increases the strength and hardness of metals, improving the endurance of the product. Copper and chrome plating are finishes commonly used for this purpose in industrial applications, including on tools, hydraulic cylinders, and mechanical products. This is particularly important in the aerospace industry as aircraft components can be costly to replace in the event of a failure in service.

 

Enhanced Appearance

Metal finishing can be achieved using a variety of methods, including silk screening, e-coating, powder coating, anodizing, and plating. The improvement to the overall aesthetic of the metal product, regardless of the procedure used, is the process’s greatest advantage.

The procedure helps to get rid of any sharp edges, clean, and then smooth the surface. A matte, glossy, or textured surface might be found on the finished product. This sophisticated method 

 

Disadvantages Of Plating

  • Subject to cracking and chipping in hard-wearing environments,
  • It can be a lengthy process as many of our finishes are subsequently hand-polished to achieve the desired high-quality effect,
  • If not managed carefully, the process can show surface imperfections such as pitting marks or scratches. This is even more profound in cheaper metals.

 

Types Of Plating

The types of plating include: 

 

Zinc Plating

As earlier described, zinc plating is one of the most durable metal plating available. Zinc is an inexpensive material that is used to provide a galvanized coating on many metal substrates. In addition to being electroplated, the element is applied by way of the Sherardizing process, by molten bath dipping, and by spraying. In the electrolytic or cold process, the article to be plated is set up as a cathode in an electrolytic bath of soluble zinc salts together with an anode of metallic zinc. The process produces a highly ductile coating of pure zinc whose thickness and uniformity can be precisely controlled.

 

Cadmium Plating

In the past, cadmium plating was frequently applied to many automotive parts and utilized as a zinc alternative. Its sacrificial protective qualities and natural lubricity for components that were regularly removed and reinstalled led aircraft makers to specify it. It was especially well adapted to marine situations since it can withstand both fresh and salt water. Although it is still accessible, its use as a plating material has decreased over time due to safety concerns. Zinc-nickel alloy plating has become popular among aircraft producers.

 

Chrome Plating

Although chrome plating is frequently only used for aesthetic reasons, it also promotes increased corrosion resistance and hardness, making it ideal for industrial applications where wear is a concern. Hard chrome plating, as it is known in this context, is occasionally used to restore tolerances on worn-out components. In the manufacture of steel furniture, car trim, etc., chromium is most frequently plated over nickel. 

There is no anodic activity because nickel is typically plated over copper, and the combination of these three elements simply prevents the underlying metal from corroding by restricting air and moisture. In order to achieve adequate corrosion protection, the platings must be appropriately applied.

Hexavalent chromium, a chromic acid, is most frequently used in the electroplating process known as chrome plating. Another choice for industrial uses is trivalent chromium baths, which are mostly made of chromium sulfate or chromium chloride.

Chromate is occasionally applied on top of zinc plating to protect the zinc and, in some situations, change the color of the metal, as in the case of green or black zinc plating.

 

Nickel vs chrome

 

Nickel Plating

Because it works well in electroless plating, nickel is a common plating metal. For better ornamentation and wear resistance, household items like doorknobs, silverware, and shower fixtures are frequently nickel plated. Nickel plating serves as the underlying plating for chromium and frequently bonds with copper and aluminum, as well as a wide range of other metals.

An alloy made of nickel and phosphorus is utilized in electroless plating. Phosphorus concentrations in the solution can range from 2 to 14%. Phosphorus concentrations that are higher improve hardness and corrosion resistance. Lower phosphorus concentrations provide greater solderability and magnetism.

 

Copper Plating

Another common plating material for uses requiring excellent conductivity and cost-effectiveness is copper. As was mentioned before, copper plating frequently acts as a strike coating pretreatment for subsequent metal platings. Additionally, it is a widely used plating metal for electronic parts like printed circuit boards. Copper is one of the less expensive metals to plate with because of its high plating efficiency and cheap material cost.

There are three different methods for copper plating: acid, mildly alkaline, and alkaline. Superior throwing power is provided by higher alkaline levels, but these values also call for lower current densities and more stringent safety measures. It is crucial to keep an eye on these levels since cyanide in alkaline copper baths has been connected by health inspectors to a number of health risks.

 

Gold Plating

Gold is prized for its high resistance to oxidation and electrical conductivity. Gold plating, which differs from gilding in that the gold is not a foil, is one of the simplest ways to impart these characteristics on metals such as copper and silver. 

The procedure is frequently used to decorate jewelry and to increase the conductivity of electronic components like electrical connectors.

The easiest way to avoid tarnishing when gold-plating copper is to apply a nickel strike before deposition. When deciding on elements such as the ideal bath combination and duration of immersion, also take into account the hardness and purity of the gold.

 

Silver Plating

Similar to gold, silver is used in plating processes where enhanced electrical conductivity and aesthetic appeal are required. Since silver is less expensive than gold and does a better job of plating copper, it generally functions as a more cost-effective plating solution.

Humidity and galvanic corrosion are two problems that could make silver plating less practical as a plating method. Because silver is prone to flaking and cracking, which could eventually reveal the base substrate, silver plating does not perform well for applications that are exposed to high humidity.

 

Tin Plating

Food and drink packaging has long been made of tin-plated steel. Tin is toxic-free, offers a coating that makes steel form quickly (due to the lubricity it offers), welds, and solders with ease, in addition to offering corrosion resistance. The tin plate is covered in food-grade oil during the passivation process, which also enhances lacquer adhesion. To better meet the needs of the interior and exterior container surfaces to their environments, tin plate sheets can be ordered with various tin thicknesses on each face. Other packaging materials, such as paint cans and grease tins, also use a tin plate. The hot-dip method is nearly always used to create the tin plate. Electronic parts are also made with the use of tin plating.

A tin-lead alloy was typically applied over steel in terneplate, another tin-based plating, as a corrosion inhibitor. The metal is perfect for use in tin roofs since it can be painted and, with routine maintenance, last 90 years. Tin is now used over stainless steel instead of lead to create corrosion-resistant roofing that takes on a softer patina. The material has a two-times longer lifespan than copper roofing.

 

Rhodium Plating

A kind of platinum known as rhodium offers resistance to tarnish, scratching and a glossy, white dazzling luster. Rhodium plating is frequently used in the manufacture of jewelry, particularly when white gold needs to be plated. Rhodium plating is also common on base metals, including copper, platinum, and silver.

One drawback of rhodium plating is that in applications that experience a lot of wear, the protective layer of rhodium will eventually disappear. After a few years, this can result in discoloration and call for another round of plating.

 

Similarities Between Anodizing And Plating

  • Both are electrochemical processes
  • Both techniques involve the deposition of a material on a metal surface.

 

Key Differences Between Anodizing And Plating

The key differences between anodizing and plating include: 

 

Different Processing Methods

  • The cathode in electroplating is the same as the anode, which is the metal that has been electroplated. An affirmative current is an input between the anode and the cathode, and the electrolyte, which contains metal ions for electroplating, is the solution. The substance to be plated and the plating material are two separate materials. For instance, in a beryllium copper and nickel plating process, the substrate is beryllium copper, and the plating layer is nickel.
  • Anodization creates a thin film coating on the surface by subjecting the metal to chemical or electrochemical treatment. When electricity is supplied in a certain electrolyte to the treated material, which serves as an anode, a thin film will form on the surface. An aluminum oxide coating will develop on the workpiece’s surface if the aluminum alloy is oxidized. Chemical stability, resistance to oxidation and acid corrosion, and color-dying capabilities all characterize alumina.

 

Different Processing Objects

  • Most plated objects are made of metal or non-metal material. The metals nickel, chromium, tin, copper, silver, and gold, are the most frequently utilized plating metals. A term used frequently to refer to nickel plating, chrome plating, gold plating, etc.
  • Anodizing is a technique for treating the surface of a metal. A suitable electrolyte can be used to anodize the majority of metal materials, including stainless steel, zinc alloys, aluminum alloys, magnesium alloys, copper alloys, and titanium alloys.

 

Different Processing Principles

  • The cathode in electroplating is the electroplating substance. The anode in anodizing is the substance being processed. Due to the charge effect, which occurs when metal anode ions migrate to the cathode and deposit their electrons there, electroplating occurs. The metal ions in the electrolyte are continuously replenished at the same time that the metal in the anode dissolves.
  • Aluminum alloys that are simple to oxidize are used in anodizing to regulate the development of oxide layers using electrochemical processes. Halt further oxidation of the metal and improve the surface’s mechanical attributes. At the moment, anodizing technology is the most popular and effective. An aluminum alloy that has been anodized can increase surface hardness and wear resistance.
  • The thin oxide surface has numerous micropores, which allows it to absorb different lubricating fluids and makes it ideal for producing engine cylinders and other wear-resistant components. The film may be dyed into a variety of lovely colors and has a significant capacity for absorption. Anodizing can be done on nonferrous metals or their alloys. This technique is frequently employed in mechanical components, parts for cars and airplanes, radio equipment, daily necessities, and architectural ornamentation.

 

nickel plating vs aluminum anodizing

Choosing Anodizing Or Plating? Valence Can Help 

Choosing between anodizing and plating will always depend on the nature of the metal you want to plate. Anodizing works better for aluminum than many other metals. It is important to speak to a professional or request a quote. 

Valence is the industry leader in quality for precision components in the aerospace, satellite, electronics, and medical device industries. 

With unique selective plating and precision masking techniques for critical plated components, we are the leading company for satellite and UAV applications, including a proprietary process for the precision internal plating of waveguides.