Passivation with STM

Chrome-free cleaning and degreasing in our immersion and spraying system

Since November 1st, 2005, we have been complying with the applicable EU directives RoHS* (Restriction of Hazardous Substances) for chrome-free passivation/rinsing. We clean and degrease aluminum die-cast parts, aluminum components or sheets, as well as iron components and iron sheets in an alternative process on our ultramodern, CHC-free and very environmentally friendly immersion and spraying system. In doing so, we achieve equivalent conversion layers as with conventional, environmentally harmful and carcinogenic chromating. This without any loss of quality, but environmentally friendly and harmless to humans.

Advantages:

• important pre-treatment for further production steps (e.g. powder coating)
• increased corrosion protection and more durable components
• environmentally friendly process, as we work chromium-free and therefore non-toxic
• development of new application possibilities for reactive metals

Work with us as a partner. Together we do something for our environment! Environmental assessment of Stöckli Metall AG by the canton of Glarus, available for download as a PDF ↓

* RoHS = Directive on the restriction of the use of certain hazardous substances in electrical and electronic equipment

Passivation 

In surface technology, one speaks of passivation when a protective layer is formed on a metallic material. The protective layer can arise spontaneously, for example on stainless steel or chrome, or it can be produced in a targeted manner using surface technology processes. The resulting protective layer is intended to prevent or greatly slow down the corrosion of the base material.

Spontaneous passivation:

If bare metal comes into contact with air or another corrosive environment, it can – depending on its condition – corrode. For example, the precious metals gold and platinum corrode very slowly. Base metals such as zinc, iron and aluminum corrode more quickly.

Whether and how quickly metals corrode depends on whether they have a passivation layer or can create one. Chrome, for example, has a thin, invisible oxide layer. An oxide layer forms when an alloy is heated in air. It separates the metal from the atmosphere. This means: No further corrosion is possible. Chrome is therefore often used as a refinement for bathroom fittings. This keeps them shiny for years.

In addition, stainless steel itself can form a passive layer. The metal contains chromium. Chromium forms a chromium oxide layer from 10.5 percent by mass. This prevents the oxidation that causes corrosion. If the oxide layer is damaged, the bare metal is in contact with the atmosphere. However, a new passivating layer then forms automatically.

In addition to chromium, aluminium, nickel, titanium, zinc, silicon and lead can also form a passive layer. Ordinary steel cannot do that. Because: The corrosion layer – i.e. the rust – consists of a rapidly growing oxide layer. This cannot slow down the corrosion.

Targeted passivation:

In the case of materials that do not form a passive layer or only poorly, it can be worthwhile to produce the passivation using a technical process. This is particularly the case with aluminium, magnesium, cadmium, zinc and silver. The passivation not only serves to create better corrosion protection, but also creates a basis for further process steps such as powder coating. And: The passivation creates, for example, a tarnish protection for silver or a protection against fingerprints.

Non-reliance on: