Corrosion resistance is a particular characteristic of stainless steel (INOX), as well as resilience, high mechanical strength, and exceptional aesthetics. Due to its exceptional material characteristics, this material offers numerous applications, although it also proves particularly challenging for grinding tools.
What is corrosion?
Corrosion is a natural, electrochemical, or chemical degradation process of metals caused by their reaction to the environment. This process attacks the material and partially or fully destroys it.
Particularly in industrial applications, corrosion causes significant economic losses since it affects the functionality, safety, and longevity of components.
Is corrosion the same thing as rust?
Not quite. Rust is a specific form of corrosion that forms on non-alloyed or low-alloy steel due to a reaction with oxygen and moisture. On the other hand, stainless steel corrodes in a different manner.
The specialists at INOX instead use the terms intergranular corrosion, crevice corrosion, or pitting corrosion – depending on the cause or appearance. On stainless steel, rust mostly appears as a brown, porous deposit only if the surface is contaminated or damaged.
When does corrosion form?
Corrosion on stainless steel frequently forms when the protective chromium oxide film is damaged on the surface – i.e. due to mechanical impacts, thermal load, or foreign particles such as iron dust. Even aggressive media such as chloride or acidic substances can attack the passive layer.
A typical trigger: Incorrect or unsuitable grinding or brush tools that transfer foreign material or alter the surface due to excessive heat input.
Why does corrosion need to be prevented?
Not only does corrosion diminish a component’s appearance, but also its technical integrity and hygiene – which are exceptionally critical in sensitive industries such as the foodstuff industry, medical technology, equipment engineering, or the chemical industry.
It can result in leaks, loss of function or, in the worst case scenario, safety related outages .
What types of corrosion are there?
Corrosion in stainless steel appears in many different forms depending on the load, tool, and environmental conditions:
- Pitting corrosion: Punctiform surface penetration, mostly caused by chloride.
- Crevice corrosion: In tight spaces, e.g., under seals or mounting elements.
- Intergranular corrosion: Along the grain boundaries, especially after improper thermal load.
- Contact corrosion (galvanic corrosion): When stainless steel contacts base metals.
- Surface corrosion: Even metal degradation on larger surfaces.
How to prevent corrosion 1:
Use the right grinding tool
The first step in preventing corrosion begins with choosing the right tool. When processing stainless steel, it is crucial to use only the designated grinding tools – at PFERD TOOLS, they can be identified by the INOX or STEELOX label and on the corresponding pictogram.
An additional important factor: Heat influx. Excess heat can damage the protective passive coating on the surface. This is why only tools with the largest-possible grain size or precision-molded high-performance abrasives such as VICTOGRAIN, specifically designed for stainless steel, should be used.
How to prevent corrosion 2:
Ensure clean working conditions during use
A lot can also be done during the processing itself to prevent corrosion problems. Always work by pressing down gently and using oscillating movements, especially on thin-walled components. By doing so, you prevent heat-related discolorations.
Grinding tools that were previously used for steel should not be used on stainless steel. During the process, adhesive steel particles can be transferred to the workpiece – and that is precisely what can lead to corrosion later on. You should also do everything possible to prevent grinding dust or flying sparks from remaining on the tool. Flying sparks should be directed away from the tool, and the grinding dust should be removed.
How to prevent corrosion 3:
Go directly to final processing
Do not waste time after the coarse grinding – proceed immediately to final processing. This helps to ensure the desired surface quality and prevent additional effects on the passive coating.
If tarnishing or traces of oxidation appear when grinding, they must be removed by a subsequent fine grinding procedure. Ultimately: You should clean thoroughly! All mechanical processing leaves behind residues that must be removed from stainless steel by all means to restore its full corrosion resistance.