Table of Contents
Introduction to Plasma Cleaning Metals
Plasma cleaning using Atmospheric Plasma, Vacuum Plasma or even Corona, removes organic contaminants at a microscopic level and is typically used as a final, ultrafine cleaning process for applications requiring cleanliness at a molecular level.
Metals often have a good to work with surface, however it can often be the case that it’s so good that it attracts contamination easily which is difficult to remove. Other metals might be too reactive to sit around bare and exposed and oxide layers form readily, again, stopping the true bare material from making a bond.
Plasma cleaning certainly can clean contamination, and in other cases it can reduce or remove oxide layers, or build them in a quick and dense way that makes them a strong surface to work with.
5 Reasons To Use Plasma Cleaning:
Plasma Cleaning is Repeatable & Reliable
Plasma is a highly controlled and repeatable process which provides a uniform treatment that can be target specific areas or all over the part. Because plasma works without the need for chemicals, or wearing abrasives, you will get the same result each time.
The main consideration here is quality in, obviously trying to clean an old material found in a work bench is much different to cleaning a freshly machined part. Controlling incoming quality will guarantee the plasma treatment and output quality.
Plasma Cleaning is Environmentally & Operator Friendly
Plasma and corona require no consumables other than air and power, and don’t give off significant amounts of harmful gases. Ozone is a biproduct of the process but can be filtered easily.
Treatment using plasma and corona is usually performed either by automation or within a sealed environment such as a plasma chamber. Both of these options mean that either extraction can be fitted and controlled easily, or within the chamber there’s actually very little if anything being produced that requires extraction.
The systems have no removable waste and can run from power only so a renewable energy supply means they are very sensible from an environmental point of view. Most systems also use very little power, ranging from 400w for smaller systems to generally no more than 10kw even for the largest systems available.
Plasma Cleaning is a Gentle Cleaning Process Suitable for a Wide Variety of Substrates
Plasma cleaning is a highly efficient yet gentle process involving no harsh chemicals, abrasive materials or extremes of temperature.
Plasma cleans the surface of the substrate at a molecular level without affecting the bulk properties of the substrate making it suitable for even the most sensitive of substrates. As the plasma discharge is potential free, plasma can be safely used to clean sensitive electronic components ready for further processing.
Plasma Cleaning is a Fast Process
Plasma cleaning offers fast processing times with a typical cycle time in the region of 1-2 minutes for all over treatment. No further steps such as rinsing, drying or curing are required.
Atmospheric plasma and corona treatment can be used either standalone or inline and usually have a sensible speed of 5m/min, although some systems will run slower or faster depending on requirements and machine size.
Whichever cleaning method you go for, the best advice is always treat and then do. Use plasma cleaning as the final, ultra fine cleaning process to give you the absolute best surface finish as close to the further processing stage as possible to avoid recontamination.
Plasma cleaning is a simple, single stage process and can be easily slotted into most production processes with both inline systems and batch systems available.
Plasma Cleaning is Thorough
Plasma cleaning leaves a microscopically clean surface with no trace organic residue. Viewed under a microscope, the surface of even highly polished metals is highly textured with many peaks and troughs. Depending on the surface energy of the substrate, wet chemicals may not penetrate these imperfections leaving behind contamination which can adversely affect post treatment processes such as bonding or painting.
Plasma cleaning is able to penetrate even the smallest imperfections vaporising organic contamination and leaving behind a truly cleaned surface.
Considerations
From our experience, it’s nice to think that Plasma Cleaning is the holy grail of cleaning processes, but in reality as mentioned earlier, incoming quality is important and understanding that plasma and corona cleaning are ultra fine processes is key.
If you want to clean anything and everything, cleaning in this way is unlikely to be the right tool for the job on its own.
If you want to take a machined part straight out while it’s still wet with fluids, plasma will never get it clean.
The real magic happens when you combine this kind of treatment with other processes such as quick wipe, ultrasonic clean or wash process.
Plasma cleaning is an excellent way to be sure that you have a surface that’s ready for further processing. It will assist and improve adhesion of inks, coatings and adhesives while at the same time use minimal energy and need no additional resources.
Cleaning Example
To illustrate our point, we can discuss a project which really opened our eyes in which a customer had a wet cleaning process with harsh chemicals. Their process worked well but the interest was there to look at new techniques and understand their usefulness – especially to remove the need for chemicals on site.
Plasma alone, without any other cleaning performed less average, but better than nothing. Not good enough to warrant a change of process.
Cleaning using chemicals could be reduced in time or use a greener wash system, but neither worked as well either.
Processing using the existing system for twice as long did not improve performance dramatically and only lead to additional costs in running and time.
The customer decided to trial a short cycle, green cleaning solution to remove the bulk of contaminants, followed by a standard cycle in vacuum plasma. This gave a surface that was far superior to any other test method. Performance increased, time taken decreased, power consumption decreased, use of chemicals decreased and employee safety improved significantly.
The customer now uses multiple machines over several sites, saving them thousands over the years and creating a better product in the process.
Conclusion and Final Thoughts
Plasma cleaning, whether using Atmospheric Air Plasma, Vacuum Plasma or Corona treatment is a powerful tool for giving a surface finish perfect for further processing.
While this technology could be used in any industry, it usually finds its way into technical industries such as battery manufacturing, aerospace, communications and other applications where cleanliness is key.
The technology can be used on micro components such as stamped components, inline aluminium foils or large scale castings depending on the system used.
Cleaning metals is often a little more complex than processing a polymer, the original finish, oxide layers, age, next process and handling conditions can make every application unique.
