Understanding rouging in the cosmetics manufacturing
Stainless steel is a fundamental component of the cosmetics industry due to its excellent corrosion resistance and mechanical properties. However, a common challenge faced by production lines in the cosmetics and personal care industries is rouging, which can have a significant impact on both product quality and equipment integrity.
Rouging is a surface oxidation phenomenon that occurs following a disturbance to the passive layer of stainless steel.
But what exactly does it look like and why does it occur?
Rouging can occur even under optimal operating conditions. It should be distinguished from conventional corrosion. It is a natural oxidation process that can be influenced by high temperatures, the presence of a strong oxidising agent, and corrosive water.
There are 3 different types of rouging:
- CLASS I ROUGING - MIGRATING
The oxide deposit is predominantly red. It has a powdery/pulverulent appearance. The particles generated upstream are oxidated and redeposited on the surfaces (stainless steel, filter...). The stainless steel under the deposit is not degraded. In this case, the deposit can be removed by wiping (test with white wipe).
- CLASS II ROUGING - NON-MIGRATING
This type of rouging corresponds to a degradation of the passive layer and to an oxidation in depth of the stainless steel. The initial passive layer has been replaced by a surface layer of red iron oxide (hematite Fe2O3)
- CLASS III ROUGING - NON-MIGRATING
This is a type of rouging which also corresponds to a degradation of the passive layer and oxidation of the stainless steel. In this case, iron oxides have a black colour with a mat or shiny appearance (magnetite Fe3O4).
Both Class II and III can only be removed with a specific chemical treatment.
Why should the cosmetics industry be concerned about rouging?
In cosmetics manufacturing, where cleanliness and product integrity are so important, rouging poses significant risks for the following reasons
- Maintaining the cleanliness of equipment: Visible degradation stains raise concerns about the hygiene and maintenance standards of the equipment and its structural integrity.
- Particulate contamination: Detached rouge particles can contaminate products, leading to safety and quality issues.
As a result of the above factors, rouging can lead to a reputational risk: by compromising manufacturing standards, it can damage the integrity of the brand and the trust of the consumer.
Prevention and mitigation strategies
Understanding the causes and effects of rouging is critical to maintaining the integrity of stainless-steel equipment used in cosmetics manufacturing. With this knowledge, proactive measures can be taken to prevent and limit the onset of rouging, such as the choice of stainless steel type and surface finish (attention must be paid to welds), the management of maintenance activities or even the implementation of periodic preventive treatments. In addition, regular inspection and monitoring allows early detection and mitigation of rouging.
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