What Is Etching On Metal?
Etching is the process through which a substrate on the surface of any object is removed. It can be done through chemical, mechanical, or electrochemical techniques.
Metal etching is therefore the process by which different techniques are applied to the metal surface to remove materials from it. Metal etching is done for purpose of adding value to that particular metal surface.
Laser Etching On Metal
Laser metal etching is the technique used to place marks, images, and shapes on the surfaces of metal parts. A great source of energy is used leading to the melting of the substrate of the metal.
The high amount of energy applied to a small area on the surface of the metal melts it and expands it. The beam of laser pulsed releases bursts of energy which are controlled at intervals, and the metal surface absorbs the energy.
Metals that can be etched through laser include carbon steel, aluminum, lead, and magnesium stainless steel.
Acid Etching On Metal
The type of metal to be etched will influence the acid to be used for the etching process. This is because some metals etch faster than others depending on the hardness level. Steels are harder and hence take longer to etch while bronze and copper are softer and take a shorter time to etch.
Moreover, the acid metal etching involves: cleaning the metal, application of the maskant, and designing the image. Additionally, you achieve this by etching through acid and removing maskant.
Electrochemical Metal Etching
This technique can be used to etch any metal that is capable of conducting electricity. It is a quick etching process that does not require heat and does not interfere with the structure of the metal.
Besides, it is inexpensive and uses electricity to etch the metals and ensures that the metal is not corroded. Again, the technique involves the use of a combination of sodium-based solutions and low voltage electrical charges.
The process can create shallow etches which take a very short time or deep etches which take a bit longer.
Photochemical Metal Etching
The technique uses a design created through a computer-aided design. Remember, the thickness of the metal and the number of pieces needed will also be calculated through a computer interface.
After the design of the image, the metal is prepared through cleaning and laminated using a photo-resistant film. The images designed through CAD are now printed on both surfaces of the metal when they are sandwiched between metals.
Then the sheets are developed and etched on a conveyer and finally, the resist film is removed through the application of a stripper.
Metal Etching Designs
The designs for metal etching can be simple or complex because the process is capable of producing any kind of design. All the manufacturer has to do is to feed in all the details needed for the design through a computer interface.
There are countless designs that can be etched and some of the designs are listed below.
- Electrical connectors design.
- Design for bipolar plates
- Micro springs designs
- Microphone diaphragm design
- Surgical tools design.
- Metal lids designs.
Metal Etching Process
1. Check On Safety
Since some chemical etchants are toxic, safety glasses can be used to protect the eyes, and gloves for hand protection. Aprons can be for body protection and be sure to put on long sleeve shirts and if necessary, wear a protective mask. It is necessary to follow all instructions issued on the chemical packaging.
2. Cleaning Process
Cleaning is done to remove dust, dirt, grease and oil stains from the metal surface. Degreasing can be done through electro-degreasing which will remove oil and oxide film completely from the surface.
Oils or grease can also be removed by use of a chlorine-based cleanser. Use a fine sand paper or a wire brush to prepare the surface of the metal making sure not to scratch the surface of the metal. Then use water to completely rinse the metal surface and use isopropyl alcohol to wipe it.
3. Pasting Silkscreen Ink Or Dry Film Photosensitive Adhesive Layer
The choice for a photosensitive adhesive layer will depend on the type of metal, the thickness of the metal and dimensions. Additionally, the layer could be thicker or thinner depending on the time requirement for the etching process.
The photosensitive adhesive layer must be dried awaiting the exposure process. At this point, ensure that there are no impurities and that the surface is clean.
At this stage, the metal is exposed an external energy which is determined by the thickness and precision of the metal. The exposure will show if the etching process will ensure good dimensional control and accuracy.
6. Creating The Design
Again, the design is then created by hand using tools that are sharp scratching off the resist in all parts that require dark lines. This creates a pattern on the surface which will be etched using a given technique. Currently, most people use electrical tapes or nail polish or permanent markers for covering the parts that will remain light.
At this stage, the type of the metal that is to be etched will determine the type of the chemical bath to be used. For instance, if the metal is copper, then you will need to use a mixture of ferric chloride and water.
If the metal is steel then the best choice of chemical is hydrochloric acid, sulfuric acid or nitric acid. The pattern on the metal gets deeper when left in the chemical bath for a longer period of time.
8. Cleaning The Etched Metal
Once etching is done to level required, the metal is removed from the bath and the action of the acid is stopped. It can be dipped in water or baking soda and then the resist is removed from the surface of the metal through a chemical.
Acetone can be used to remove nail polish, alcohol to remove wax, and turpentine to remove varnish.
Once the etching process is over and the metal product has been removed and cleaned, at detection process takes place. A follow up test is done to confirm if the final product was able to meet all the specified requirements.
There are various tools available in the market that can be used for metal etching purposes.
Some of these tools are described below.
Used for creating fine lines on the metal surface and they come in various sizes and different levels of sharpness.
Used to create an area of tone on the metal surface by rolling this tool over the metal in different directions.
A scrapper is used for removing any marks on the metal surface and to make smooth the edges that are rough.
This tool is used to remove any kind of unrequired lines on the metal surface.
The tool creates large areas of tone, this forms rich velvety black sections on the metal surface.
Benefits Of Etching On Metal
The metal etching process is precise and accurate therefore limiting errors and the need for further finishes.
Since the process is digital, all errors are eliminated at the design stage.
Process is digitally controlled meaning any design can be etched on the metal.
Once a design is done, the etching process produces the exact image on the metal surface.
Also, the etching process does not alter the chemical or physical properties of the workpiece.
This is because it does not create any kind of stress on the metal during etching.
It is important that all the similar parts produced etching possess the same dimensional tolerances.
Since the digital diagrams and renderings are not changed for all runs, this is possible.
Metal etching is a very fast process especially if it is a laser metal etching technique in use.
It also does not require secondary finishes saving on time and money.
The metal etching process does not involve deforming the metals and does not tough them in any way.
This creates products with tight tolerances and do not need other finishes.
Branding can easily be done on products through metal etching processes.
And the branding can be included in the general design for the etching process eliminating the need for labels.
Creation of phototypes allows the client to see the exact design that will be produced.
The designer is able to make changes as needed before the actual etching takes place.
Choosing Metal Etching Chemical
Before choosing the type of chemical to be used for the metal etching process, consider the following factors.
Type Of Metal To Be Etched
Different metals can be etched using various chemicals, for instance, stainless steel can be etched using ferric acid. The choice of chemical must suit your type of metal.
Strong acids etch the metals in a short period of time while weak acids do this in a longer period of time. Again, the speed at which the metal is etched should be an important point of consideration.
Versatility Of The Chemical
The need to carry out several runs on the same chemical will require a versatile chemical that can allow all the runs.
Cost Of The Chemical
The chemical of choice should be pocket friendly to be able to cut on cost for both the manufacturer and the customer.
Some chemicals are extremely toxic and may not be easy to handle. It is important to choose a chemical that will be easy to handle and ensure safety to the environment and users.
Metal Used In Metal Etching
Series 625 is the type of Inconel metal that is mostly used for etching processes. The metal is tough and is usually very difficult to etch, however, there is a special etching process meant for Inconel. It is used to make bipolar fuel plates and other applications used in extreme condition because it can resist corrosion.
Nickel alloys are widely used in applications such as electrical and they are easy to etch. They offer high resistance to corrosion and heat. Besides, the metals are versatile and resist temperatures of up to 932° F or 500° C.
These alloys are durable, conductive, malleable and ductile making them suitable for both two- and three-dimensional electronics.
This is the best candidate for laser metal etching technique. 316 and 306 series are the most used grades of stainless steel in metal etching.
Aluminium is resistant to corrosion and has less weight making it suitable for applications in aircraft, and ships. It is mostly used with laser metal etching technique.
This metal has great properties like strength, corrosion resistance, light weight. It is difficult to machine, but very easy to etch because of its high thermal conductivity.
Metal Etching Products
Metal Covers And Lids
Etching is used to create these covers and lids in order to create tight and precise lids and can accommodate required dimensional tolerances. This is easy because the metal etching process does not interfere with structure of the metals being etched.
The metal etching process can produce electrical connectors that are free of stress and burr. Again, the metals used for these products must be of high performance with great strength to weight ratios.
Metal etching is needed for making medical instruments such as prosthetics for implantation and surgical tools.
Parts of an automobile like clutch springs, fuel cell plates, nameplates and encoder disks are created through metal etching. Metal etching is able to create parts with precision to the smallest detail and is therefore popular with automobile industry.
This is the device used for changing vocal waves into electronic waves. Since the microphones are very small, they also need smaller diaphragms and this is not easy to produce. However, metal etching has become the ultimate solution for such challenges because it can work with very small parts.
Micro springs can easily be produced through metal etching since it does not deform the metal. There are so many applications including the medical industry that require the use of these micro springs.
Metal etching is preferred for creating bipolar plates because they can make the intricate parts in a smooth and efficient process. The process allows for adjustment of size and shape of the plates as desired.
For any questions or inquiry on etching on metal contact KDMFAB now.