Chemical Focus
Parts cleanliness: choice of cleaning agent is key
In many industries parts cleanliness has become an important quality criteria. Defined cleanliness specifications have to be fulfilled. Doris Schulz reports.
In vielen Branchen ist die Bauteilsauberkeit zu einem wichtigen Qualitätskriterium geworden. Es sind festgelegte Sauberkeitsvorgaben zu erfüllen. Doris Schulz berichtet.
Dans de nombreuses industries, la propreté est devenue un critère de qualité important. Il faut satisfaire à des spécifications de propreté détaillées. Doris Schulz témoigne.
M
anufacturing and processing metallic parts is inevitably connected with dirt on the part’s surface
afterwards. These contaminations, such as machining oil and emulsion, usually influence the quality of subsequent manufacturing processes, for example coating, welding, bonding, and assembling, and may impair the functionality of the finished product. Thus, the task of industrial parts cleaning is to fulfill requirements for parts cleanliness that result from downstream processes. Mostly wet- chemical cleaning techniques are used for that purpose. Quality, cost-efficiency, stability
and processing time of industrial parts cleaning operations critically depend on the dissolving capacity of the used cleaning agent. The most frequently used agents
are aqueous detergents and solvents. In selecting the right cleaning medium, the ‘equal dissolves equal’ principle of chemistry applies. In other words, for water-based (polar) types of contaminations such as coolant and lubricant emulsions as well as for
removing solids such as chips, salt, residues of polishing pastes and particles, aqueous cleaning agents are typically the first choice. They are available in neutral pH, alkaline and acidic formulations. It is advisable to test compatibility with the part material and the achievable result by cleaning trials beforehand. To ensure a consistent cleaning performance, aqueous processes should be subjected to regular process monitoring, with control of key process parameters such as detergent concentration, temperature, rinse water quality and filter condition. When removing mineral oil based, non-polar contaminations, e.g. machining oils, greases and waxes, a solvent is commonly the preferred cleaning agent. When washing away the oil, swarf and particles, the components will lose their adhesion which then can be removed mechanically, e.g. by ultrasonic cleaning or injection flood washing. Some traditional applications for
solvent cleaning are:
n Cleaning of heavily oiled contaminated parts that would require extensive conditioning efforts and lead
Fig. 1. Choosing the cleaning agent according to the principle ‘equal solves equal’, does not only offer technical and economical, but also ecological advantages.
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