For many high precision industries such as aerospace, automotive or medical technology, industrial parts cleaning plays a crucial role in quality assurance during the production process. Inadequate degreasing can have a detrimental effect on many subsequent processing steps. Nevertheless, we see far too many companies using a suboptimal cleaning solution in their operations.

Some businesses simply lack the knowledge to competently evaluate potential options. Others have relied on one particular method for so long that they are not aware of alternative solutions. And in many cases, deep-seated misconceptions about a particular cleaning technology lead to a categorical exclusion of its use.   

One example in point is solvent cleaning. Many manufacturers are coming under significant corporate pressure to move away from solvents to water-based cleaning in the name of achieving greater safety and sustainability. What is troubling is that sweeping decisions are often made based on a distorted view of how solvents and water-based cleaning work. 

The truth is every cleaning system has its own environmental impact that manifests itself in different ways. Whether it is solvent or water-based cleaning, both processes require prudence and diligence from users to ensure worker safety, environmental protection and regulatory compliance. Making an informed decision means evaluating all the facts, data and key aspects objectively. And that must start with overcoming preconceived notions.  

Cleaning efficiency – is one better than the other? 

Both solvent and water-based cleaning are effective, but the evaluation of their use must be tied to the specific context. Water-based cleaning can be an excellent choice for polar contaminants like salt residues. The process can be more efficient when working wet in wet (e.g., water-based painting, galvanisation). Depending on the pH, it does not affect rubbers, plastics, or painted surfaces. Cleaning can also be combined with surface treatments such as phosphating, chromating or the application of protective coatings. Because of the different formulations available, water-based cleaning can also be adapted to specific cleaning requirements. 

Solvents, on the other hand, are the first choice for cleaning off non-polar contaminants like oils and greases. They are also universally compatible with metals (please note that water-based cleaning agents can be acidic, neutral or alkaline and are usually matched to specific metal types). Because of their good creeping properties, solvents are particularly suitable for cleaning complex geometries or tiny parts. 

What is the environmental impact? 

Many people tend to associate water with “being green”. However, water alone cannot completely clean off contaminants. Most water-based cleaners contain surfactants, biocides, complexing agents, dyes, fragrances, etc. Some of these compounds are not biologically degradable and, depending on their concentration, may be harmful to flora and fauna in surface waters.

Not to forget that water itself is a finite resource. Water-based cleaning also comes with significant energy demand. There is the need to operate high-pressure pumps, heat the cleaning water, dry the metal parts, as well as treat and purify used water for re-use or disposal. As a relatively slow-drying cleaner, water requires 10 times more latent heat of vaporisation (2259 J/g) than solvents (200-300 J/g).

Solvents, in contrast, have good drying behaviour and can easily penetrate into confined spaces. Of course, such properties can also bring inherent risks such as air emissions or ground penetration. The use of modern, closed machine technology, in combination with a closed-loop solvent delivery system, is therefore the key to emission- and spill-free transport, storage and handling of solvents.

Solvent cleaning does not require heaters or blowers, as the vacuum condition allows parts to readily come out dry from the cleaning machine. Through built-in distillation in closed cleaning machines, solvents can be continuously recycled and less waste is generated. The most modern solvent systems with up-to-date solvent management practices can remove 100 kg of oil using less than 15 kg of solvent1. In comparison, a water-based system requires approx. 100 kg of water-based cleaner  to clean off 100 kg of oil.

What is the cost of ownership? 

The true cost of ownership must take into account – in addition to the acquisition cost – long-term operating expenses such as chemicals, utilities bills, floor space, and waste disposal charges.  

Standard solvent machine technology and initial chemicals often require a higher capital investment than water-based cleaning. But solvents can be continuously reused and recycled via the machine’s distillation unit. This results in much lower solvent replacement volumes and fewer bath exchanges. In aqueous cleaning, since dirt and soils are emulsified and rinsed off, aqueous baths that are not treated must to be replaced frequently. 

Another key cost factor is the labour time for operation and process monitoring. In solvent cleaning, only stabilisers are added (when necessary), so the chemistry in the vapor degreaser remains relatively constant and requires little attention to ensure a consistent cleaning performance. In water cleaning, various chemicals such as builders and surfactants are added to make the cleaning of non-polar contaminants possible, their concentration therefore requires constant monitoring and adjustments.  

The bottom line …

Every cleaning process comes with its unique requirements and challenges. Solvents are by no means a one-size-fits-all solution. However, companies would be doing themselves a huge disservice if they immediately rule out solvent cleaning without an objective evaluation. More than a necessity, parts cleaning can contribute to operational efficiency, resource conservation as well as sustainability – but it all depends on making the right, informed decision. 

Sales Manager Mexico SAFECHEM  

SAFECHEM Europe GmbH Tersteegenstr. 25 40474 Duesseldorf, Germany

Tel. +52.55.8078 4049

E-mail: o.vega@safechem.com 

www.safechem.com