The welding dilemma

Stainless steels are corrosion resistant due to a thin passive coating of chromium oxide. Heat during welding destroys this layer; the surface is then susceptible to corrosion. Tarnish colours and oxidation layers must therefore be removed after welding and the surface must be repassivated.

This is done either chemically or mechanically. Chemical cleaning by pickling is poisonous, requires long exposure times and leaves unsightly pickling edges. Mechanical methods by brushing or grinding are not poisonous – but mostly leave ferrite or iron oxides on the surface that cause new rust. Blasting methods, on the other hand, are associated with high vibrations.

All methods have a major common disadvantage: The surfaces must be passivated in a further work step. This can be done either by storage under controlled air humidity and oxygen supply conditions, or with the aid of a passivation agent that will again affect health and the environment.

Magic? No – electrochemistry!

Our newly developed method cleans and passivates metal surfaces electrochemically using high-current electric arcs – in one work step! The user wets the work piece with non-poisonous electrolyte fluid and passes a carbon fibre brush over it – millions of electric arcs do the rest.

A similar principle has already been applied for two decades with the tampon method, which is based on moving a piece of electrolyte-soaked felt on a carbon electrode. However, this method never grew beyond a niche market, due to the low electrical output and the small contact area of the electrode.

Only our newly developed carbon fibre brush in combination with new, high-power device technology have made this intelligent electrochemical method with all its advantages suitable for industrial applications.

Cleaning with carbon fibres

Carbon fibres are excellent conductors. Our carbon fibre brush contains up to 1.5 million of them; they conduct high current to the work piece with a current density of up to 250 A per cm². Electric arcs form at the tips of the carbon fibres – similar to the process in TIG welding. These millions of small electrical charges are electronically limited to a length of 5 μm. They remove tarnish colours, oxidation layers and even minor scaling at lightning speed without damaging the surface.

The electrolyte liquid is used to increase electrical conductivity and provide cooling. Evaporation generates a protective gas atmosphere that protects against new corrosion. The split-off oxygen forms chromium dioxide during the cleaning process – which restores the protective passivation layer! This effect was confirmed for us by the IGOS Institute in Solingen after standardised tests with salt spray.

The cleaning effect is not achieved by etching or pickling – as is the case with the devices made by our competitors – but almost exclusively through the extremely high energy density. Our cleaning electrolyte is the non-poisonous E338 food additive – which is also used in cool drinks.

The fibres of the carbon fibre brush hug the shape of the work piece during the cleaning process; different brush sizes, shapes and types make any cleaning task easier. Flexible extension of fibres from a Teflon sliding sheath can be used to reach corners and gaps. And our patented in-pipe brushes allow pipes and holes to be cleaned from the inside.

Mirror-smooth polish

Our switchable AC/DC devices also facilitate direct current (DC) mode for high-gloss polishing. Strong discolouration can be removed or evened out and dull areas in the heat-impact zone can be treated to the desired level of gloss.

Forgery-proof marking

A writing template or label printer can be used to produce individual signatures on your work pieces. Dark marking applies an oxidation layer to the surface; bright marking removes parts of the surface – like engraving, but does not look dark. Both methods are permanent and resistant against chemicals and abrasion – and are therefore often used for surgical instruments, tools, sanitary fittings, etc.