Have you considered these top 3 questions when selecting your cleaning agent?

Choosing the right cleaning agent for your application is crucial to ensuring optimal cleaning results. Insufficiently cleaned parts can affect the quality of many subsequent industrial processes such as coating, welding, bonding and assembling. This can have a detrimental effect on the functionalities of the parts. Particularly in high value manufacturing sectors such as aviation and defence, medical technology, and motor vehicles, cleaning quality is not only synonymous with quality, but reliability and even safety.

To make an informed decision, begin with these three important questions:

1. What are your cleaning requirements?

Understanding your required cleaning quality is a critical first step. To achieve optimal cleaning results, it is important to consider two types of contaminants: 

• Particle contaminations (e.g. their size, numbers, and types) and
• Filmy contaminations. 

Aqueous cleaning agents have a density of approx. 1g/ml. Solvents, in comparison, may have a higher or lower density. “Heavier” cleaning agents are effective in removing particulates that cannot be readily dissolved. They can literally “push” or ”float away” particulates and lift them off the surface.

Different industrial applications also require varying levels of surface energy of the metal surface, which is influenced by filmy contaminations. For instance, processes like nitriding or crack detection demand higher surface energy compared to standard coating or assembling. Therefore, the required surface energy should match the ability of the cleaning agent. For precision cleaning where required surface energy can range from 38 mN/m to 60 mN/m, both aqueous-based cleaning and solvents are capable of fulfilling the requirement.

It's important to note that in aqueous cleaning, as soils and contaminations are emulsified and flooded off the surface which remain in the water (unless specific procedures are performed to purify the water), the quality of cleaning will mainly depend on both the quality and the number of the rinsing baths with demineralized water. The higher the required quality of cleaning, so do the investment and space requirements for aqueous systems. 

Generally speaking, optimal cleaning result depends on the properties of the chosen cleaning agent, such as density, polarity, surface tension, solvency power, viscosity as well as its capacity for carrying soils.

2. What is the affinity of the cleaning agent to the contaminations?

Different contaminations require different cleaning approaches because of their distinct chemical and physical properties. The principle "equal dissolves equal" applies here; just as a key only fits into its matching lock, the cleaning agent should be chemically similar to the contamination to dissolve it effectively.

Polar vs. Non-Polar Contaminations

Polar (inorganic) contaminations, such as coolant and lubricant emulsions as well as solids like chips, salts, residues of polishing pastes  are ideally cleaned with water-based agents. These are available in neutral pH, alkaline and acidic formulations, as well as in a wide variety of surfactants and other ingredients. Non-polar (organic) contaminations, such as  oils, waxes, greases are more effectively cleaned with solvents.

Nowadays modified alcohols are also available; due to their both non-polar and polar properties, they are able to clean non-polar contaminations as well as certain polar contaminations. This type of solvents has a much broader application range compared to traditional non-polar solvents.

3. What metal types are you cleaning and how are they configured?

• Are you cleaning just one metal type or different kinds (e.g. iron, brass, copper, aluminium etc)? It is important to take into consideration the metal types you are cleaning, the size of the parts, and their configuration.
• What is the size of the parts? Are you cleaning large components ortiny parts, like a ball pin?
• What is the configuration of the parts? Do you have parts with complex geometries, such as blind holes? 

In water-based cleaning, the cleaning agents – which can be acidic, neutral, or alkaline – are typically matched to specific metal types. Cleaning different metals simultaneously can therefore be challenging and may lead to compatibility issues, and in worst case: corrosion. Sometimes, reactive additives are introduced into the water to modify metal surfaces in processes like etching and pickling. At times such reactive additives can also act aggressively on certain metal surfaces where it is not intended.

On the other hand, solvents offer broad material compatibility, making them suitable for universal cleaning across all types of metals when used properly.

For components with tiny or complex geometries, or small crevices, solvents are often recommended due to their lower surface tension and viscosity. Such characteristics  allow them to easily penetrate and evaporate from tight spaces. With water-based cleaning, even tiny traces of residual moisture can lead to problems, such as challenges in subsequent production processes, corrosion, or the growth of bacteria and related bioburden issues. 

Of course, in addition to these technical considerations, you should also take into account economic, safety and sustainability factors when selecting the right cleaning agent.  However, these three questions will provide you with a solid starting point.