What Is Chrome Plating?
Chrome plating,also known as chromium plating, is an chromium electroplating process in which a chromium layer is deposited on a metal or an alloy base.
Besides enhancing the aesthetic appeal of the machining components with a shiny and mirror-like surface, this technique also significantly increases its durability.
Chrome plating improves surface hardness and durability. Besides it also reduces corrosion and is easy to clean. All the advantages above make it use in several areas for aesthetic and mechanical purposes.
Typical Materials for Chrome Plating
Hexavalent Chromium
Hexavalent chromium, one of the common chrome plating materials, is mainly derived from chromic acid (CrO3). When being dissolved in water, the chromic acid (CrO3) forms H2CrO4 after adding sulfuric acid (H2SO4).
It is widely used in both decorative and hard chromium plating because of its excellent corrosion,wear resistance and high hardness.
However, the substance is toxic, which poses environmental and health risks to the people around the area. Therefore, the hazardous waste from hexavalent chromium baths has to be treated before disposal.
Trivalent Chromium
Trivalent chromium plating is produced with chromium sulfate or chromium chloride mainly.
Considered as a green chemistry solution to hexavalent chromium. trivalent chromium is employed in the decorative chrome plating and some of the industrial purposes.
It is less toxic and more environmentally friendly as compared to hexavalent chromium. But, like any other chemical, the usage and disposal of any waste containing Trivalent chromium are also regulated.
The Steps of Chrome Plating
Chrome plating is a technique of applying a layer of chromium to a metal or plastic parts to give it a better look and longer lifespan. The chrome electroplating process consists of several steps to ensure a smooth and durable coating.
1. Surface Preparation
The first process that needs to be done is surface preparation in order to guarantee the right bonding of the chrome layer. This involves:
- Cleaning and Degreasing: Using different cleaning processes like emulsion cleaning, alkaline cleaning, solvent cleaning to cleaning the surface free from all kinds of deposits like dirt, grease etc.
- Polishing: Sanding or buffing the surface to the finest possible and reducing the roughness depth to Rz 2-3 μm to make sure that the chrome layer will stick well and give enough protection.
2. Etching
In the case of non-metallic meterial such as plastic, the surface need to be etched so as to provide a rough surface for following layers of the coating to bond with. In this process, the parts is submerged in an etching fluid which can be hydrochloric, hydrofluoric or sulfuric acid.
3. Neutralization
After etching, the parts is washed and neutralized to eliminate the residual acids for the following processes. This is normally achieved with the help of a neutralizing solution.
4. Catalyzing and Accelerating
However, for the plastic substrates, it need to have a catalyzing and accelerating process in order to enhance the surface for the electroless plating process. This involves immersing the parts in a liquid which has a catalyst in it like palladium chloride.
5. Electro-less Plating
There is always a initial step of electro-less plating of nickel or copper before the actual chrome plating begins. This layer is used as the base for the following electroplating process to take place.
6. Electroplating
The core of the chrome plating process involves:
- Immersion in Electrolytic Bath: The parts is placed in the electrolytic bath with chromium ions dissolved in it.
- Application of Electric Current: An electric current is passed through the bath and this causes the chromium ions to be deposited on the surface of the parts and this results to a solid chrome layer.
- Temperature Control: It is normally done at temperatures of between 50-60°C so as to enable good deposition of the antigen.
7. Rinsing and Polishing
After the chrome layer has been deposited:
- Rinsing: The parts is then washed so as to eliminate any of the chemicals that may still be present in the plating bath.
- Polishing: The plated surface is sanded in order to smoothen and provide with the required shine. This more typical for decorative chrome plating.
8. Inspection and Quality Control
Last of all, the parts is examined to check if the chrome plating is uniform and if there are any defects on it. Any additional refining that may be required is done here while any following polishing is also done here.
Types of Chrome Plating
Hard Chrome Plating
Hard chrome plating is also referred to as industrial chrome or engineered chrome. Standard hard chrome thickness is between 0.02mm and 0.04mm. It is mainly applied for the performance characteristics that offers in most of the applications.
This type of plating is characterized by the high hardness, wear resistance and low coefficient of friction. In this process, it is mostly used on machine parts, hydraulic cylinders and automobile parts in order to increase their durability and efficiency.
There are a variation of hard chrome. it is called Thin dense chrome. and offers enhanced durability with lower friction and higher corrosion resistance, ideal for precision applications.
Characteristics:
- High hardness (ranging from 750 to 1000 Hv).
- Excellent wear resistance
- Low friction coefficient
- Good corrosion resistance
- It is normally greater than 20 micrometers.
Applications:
- Hydraulic cylinders
- Piston rods
- Industrial machinery
- Automotive parts
Decorative Chrome Plating
Another type of chrome plating is the decorative chrome plating or commonly referred to as bright chrome or show chrome. It is mainly used for ornamental purposes. It gives a smooth surface and a metallic appearance that makes the plated parts to have a mirror like surface.
This type of decorative chrome plating standard thickness range is between 0.002mm and 0.02mm. It is thinner than hard chrome and is normally applied in conjunction with other layers such as nickel to enhance the bond and corrosion protection.
Characteristics:
- Shiny, mirror-like finish
- Thin layer （thickness less than one micrometer）
- This one is usually used together with the nickel layers
- Moderate corrosion resistance
Applications:
- Automotive trim and accessories
- Household fixtures
- Furniture
- Consumer electronics
The Difference Between Hard Chrome and Decorative Chrome Plating
Although both hard chrome and decorative chrome processes use chromium, the two are different in their functions and properties.
Hard Chrome Plating
Industrial chrome or hard chrome plating is used more for the performance characteristics of the part rather than the appearance. It is intended to enhance the life expectancy of the parts of the machine as well as their efficiency.
Some of the uses include hydraulic cylinder rods, piston rings, molds, dies, and other mechanical parts that have to undergo high wear and tear and low friction.
Characteristics:
- Thickness: Hard chrome plating is much thicker than decorative chrome and is normally between 0. 0002 to 0. 020 inches. This thickness is beneficial in offering improved wear resistance and durability of the material.
- Hardness: It is extremely hard, ranging between 65 to 69 HRC, this makes it suitable for use under harsh industrial environment.
- Surface Finish: Although it is metallic and shiny, hard chrome does not possess a leveling effect; in fact, it tends to exaggerate surface imperfections and roughness. Hence, it is not employed for aesthetic functions.
Decorative Chrome Plating
Decorative Chrome Plating is mainly used to beautify parts since it possesses a shiny surface. It gives a smooth, reflective and glossy surface that gives a good look to the structure.
This type of plating is normally applied on automotive trimmings, household utensils, hardware, musical instruments, and other consumer products.
Characteristics:
- Thickness: Decorative chrome plating is thinner than hard chrome plating is thicker, it could be as thin as millionth of an inch. This thin layer is enough to give a shiny and reflective surface without increasing the thickness of the material.
- Layering: The process normally includes electroplating of a layer of nickel on the item before plating with chrome layer. The nickel layer gives the appearance of smoothness, shine, and rust-proofing while the tiniest chrome layer gives a slight tinge of blue and extra protection against abrasion and rust.
- Ease of Cleaning: The chrome used in the decorative products is smooth and easy to clean and therefore ideal for home use.
| Comparison Table | ||
| Feature | Hard Chrome Plating | Decorative Chrome Plating |
| Primary Use | Industrial applications | Aesthetic enhancement |
| Thickness | 0.0002 to 0.020 inches | Millionths of an inch |
| Hardness | 65 to 69 HRC | Not specified |
| Surface Finish | Emphasizes surface defects | Smooth and reflective |
| Layering | Single layer of chromium | Nickel layer followed by thin chrome |
| Applications | Hydraulic rods, piston rings, molds | Automotive trim, household fixtures |
| Ease of Cleaning | Not specified | Easy to clean |
How to Remove Chrome Plating?
There are 3 ways to let you know how to take chrome off
Specialist Equipment
First, the use of specialist equipment remains the most expensive but effective method. Choosing this approach means hiring a well-experienced person who specializes in stripping chrome plating.
Abrasive Blaster
The process of abrasive blasting need to use high-pressure air to propel abrasive materials including sand, glass beads or steel shot to a surface. This technique is applied to remove the chrome or other type of finish on car parts while leaving the metal base untouched. Despite this, it has some dangers such as breathing in dust, chances of getting an eye injury, and skin rash.
Ultrasonic Cleaner
Another equipment-based method is the use of an ultrasonic cleaner, which is mostly for washing delicate products such as electronic parts or jewelry. It uses high frequency sound waves to clean the surface by removing dirt and other stains.
For chrome, it vibrates the chromium particles vigorously and this makes them to let go of the metal. This method is easy and non-intrusive. Because of the cleaner’s size, it is best used on small items.
Using Chemicals
Chemicals are cheaper than mechanical methods of chrome removal but they pose serious health risks. Hence it need protective gear when using them.
Hydrochloric Acid
This corrosive substance is also used to remove rust and commonly referred to as muriatic acid. To remove chrome, a fluid with 30–40% concentration is enough. The chrome-plated parts should be soaked in a fluid in a strong metal pan until the chrome comes off. This fluid is mixed with hydrochloric acid and water in the ratio of 1/3 acid to water.
Sodium Hydroxide
Also referred to as lye or caustic soda, sodium hydroxide is potent for chrome removal but releases highly explosive hydrogen gas, if it reacts with aluminum.
- Mix 8 to 12 fluid ounces of lye with a gallon of water in a neutral container.
- Soak the item until the chrome is gone.
- Rinse and dry.
Reverse Electroplating
The process of reverse of electroplating is done by sulphuric and chromic acids which is dangerous because of the injuries and toxic gases. This should only be done by those who have adequate knowledge in dealing with electricity and chemicals, and it is done by passing the parts through a live current to separate the chrome.
Everyday Household Products for Diy Chrome Plating
- Baking Soda: A mild abrasive, baking soda can be used to make a paste that can be used to remove thin layers of chrome.
- Bleach: It might be possible to remove thinner coatings by soaking the chrome-plated item in a bleach solution for a day; always dispose of the bleach properly.
Conclusion
Electroplating of chromium on other metals is known as chrome plating, and it has the following advantages.
This chromed layer not only improves the looks but also increases the surface hardness, makes it easier to clean and offers protection from corrosion. It is ideal for commercial and industrial applications.
ChansMachining as your manufacturing partner is ready to provide you with the best chrome plating services. We have a team of highly experienced professionals and with the latest tooling to address your product requirements. Please feel free to contact us today to know how we can help with your project.
FAQ
What kind of materials can be chrome plated?
Chromium plating is one of the most popular technologies that involves deposition of chromium onto different substrates to improve their protection from corrosion, hardness of the surface and appearance. Some of the most used plating materials are steel, stainless steel, aluminum, copper and its alloys, brass, bronze and some plastics though these last ones need a conductive layer to be deposited first.
