Surface treatments

All our products undergo two surface treatment processes. Micro shot peening and passivation.

Micro shot peening

The micro shot-peening treatment can be performed in order to prepare the surface for subsequent treatments or coatings. The process will create an homogeneous surface while removing a thin layer of metal (around 1 µm) and creating a rough surface that will improve the adherence of following chemical deposition treatments.

In case of stainless steel objects such as our filters it can be considered a finishing treatment.

Micro shot peening is a cold deformation process. It is obtained by impacting the surfaces with spheres which can be metallic and non-metallic. The process goal is to leave residual compression forces in the superficial layer of the metal increasing the fatigue resistance.

Passivation

The second superficial treatment that we apply to our filters is passivation.

All our filters are manufactured in stainless steel. The name refers to the ability of this type of metal to resist against corrosion. A protective layer is formed on the surface of the components. The ability to form the layer is assured by the presence of chromium in the alloy. In fact in order to be considerate stainless steel an iron alloy must have a content of chromium of at least 10,5 %. The chromium creates a thin layer of oxide on the surface that prevents the surface from corrosion.

However the appearance of rust after a short period of time is not unusual.

It is interesting to know that the protective layer is only a few nanometers thick. After mechanical machining and welding small particles and areas on the surface tend to have a high free iron content and are keen to corrosion.

Passivation is a chemical process that aims to reduce the chemical reactivity of its surface. The name refers to the ability of the metal to be passive to the external environment, or less reactive. Passivation removes the free iron from the surface by using an acid solution. The other elements of the alloy, mainly chromium and nickel will react to the oxygen in the air creating a layer of oxides that protects the underlying metal from corroding.