Weld Cleaning Machine Electrochemical Weld Cleaning Machine

METOX 500 and METOX 600 are portable machines that remove weld marks from stainless steel surfaces by electrochemical cleaning. The same pass also passivates the surface; depending on the model, the machine performs electropolishing and marking as well.

The problem they solve is heat tint — the discolouration that appears after welding. The high temperature generated during TIG (argon) welding breaks down the chromium oxide layer that protects stainless steel, leaving a blue–purple–yellow band on either side of the weld seam. This is not only a cosmetic defect: the discoloured zone has significantly lower corrosion resistance than the rest of the material. In food, pharmaceutical, chemical and marine applications, the first corrosion always starts there.

Electrochemical cleaning removes that layer using a controlled electric current together with a weld cleaning solution — and at the same time restores the chromium oxide layer. In other words, cleaning and passivation happen in a single step.

METOX 500

METOX 500 is the base model. It has two functions:

1. Weld cleaning and passivation
2. Marking

It restores welded stainless steel and saves time, labour and consumables. On TIG (argon) welds it removes heat tint instantly and brings back the original colour without tone differences or dulling.

The marking system produces high-quality marks on stainless steel, galvanised steel, chrome steel, carbon steel, aluminium, brass, copper and titanium at a lower cost than laser systems.

METOX 500 technical specifications

METOX 500 set contents

METOX 600

METOX 600 is the newer model and cleans more powerfully than the METOX 500. It has three functions:

1. Weld cleaning and passivation
2. Electropolishing
3. Marking and etching

Its instant electrochemical reaction guarantees weld mark removal and surface passivation on any stainless steel surface — without downtime, swirl marks or dulling.

Thanks to DC current it performs electropolishing within seconds. Marking is carried out with an AC reaction, etching with a DC reaction.

METOX 600 technical specifications

METOX 600 set contents

How does it work?

The process relies on an electrochemical circuit established between the carbon brush tip and the workpiece:

1. Ground connection. The METOX 508 ground clamp is attached to the workpiece, completing one end of the circuit.
2. Solution. The carbon brush is dipped into METOX KTS 501 weld cleaning solution, which acts as the electrolyte.
3. Contact. The brush is moved along the weld seam. A low-voltage (14 V) current flows between the brush and the workpiece.
4. Reaction. An instant electrochemical reaction begins at the point of contact; the thermal oxide layer dissolves and is lifted from the surface.
5. Passivation. The same reaction rebuilds the chromium oxide layer on the cleaned surface.
6. Rinsing. The surface is rinsed with water; a neutralising fluid is applied where required.

The most significant advantage of the method is that it does not damage the surface. Grinding removes material, leaves swirl marks and changes surface roughness; electrochemical cleaning removes only the oxide layer. There is no colour mismatch, no dulling — the original surface appearance is restored.

AC and DC operation — what each one does

The fundamental difference between the METOX 600 and the METOX 500 is that the 600 delivers both AC and DC output. They do different jobs:

AC (alternating current) — marking. Because the current alternates, the surface undergoes a colour change rather than material removal. The result is a dark mark that is not recessed into the surface. Logos, serial numbers, material grades and CE marks are applied this way — permanent, but without breaking surface integrity. Since surface roughness is unchanged, this method is preferred on food and pharmaceutical equipment.

DC (direct current) — etching and electropolishing. Because the current flows in one direction, material is removed from the surface in a controlled way. In etching, the mark is recessed into the surface and is more resistant to wear and cleaning. In electropolishing, micro-peaks are removed to produce a bright, smooth surface.

The practical benefit of electropolishing is not only visual. A smoother surface reduces bacterial adhesion and soil build-up; cleaning becomes easier and corrosion resistance increases. For this reason electropolishing is often written into specifications for food, dairy, beverage, pharmaceutical and chemical equipment.

METOX 500 vs METOX 600

Which model should you choose?

Choose METOX 500 if: your requirement is limited to weld mark removal, passivation and marking; polishing is not part of your specification; portability on site is a priority (7.40 kg, carried in one hand).

Choose METOX 600 if: surface brightness and smoothness are a product requirement — food, dairy, beverage, pharmaceutical and chemical equipment, hygienic process lines; electropolishing is written into the specification; recessed (etched) marking is required; or your welding volume is high and you need stronger cleaning performance.

The decision rule: "Do I need faster weld cleaning?" If yes, choose the METOX 600.

Operating steps

1. Surface preparation. Remove oil, dust and heavy soil from the area to be cleaned. The electrochemical reaction does not work properly on an oily surface.
2. Ground connection. Attach the METOX 508 clamp to clean, bare metal on the workpiece. Attaching it to a painted or oxidised spot will not complete the circuit.
3. Brush setup. Fit the METOX 502 carbon brush into the METOX 503 brush holder and adjust the brush length to the geometry of the job. In tight corners use the METOX 504 Teflon sleeve — it prevents short circuits and concentrates the cleaning power on a smaller, better-defined area.
4. Solution. Dip the brush into METOX KTS 501 weld cleaning solution.
5. Cleaning. Switch the machine on and move the brush along the weld seam with steady strokes. Do not press — contact is enough. The discolouration visibly disappears.
6. Rinsing. Rinse the surface thoroughly with water. Apply a neutraliser with the METOX FPS spray bottle where required.
7. Polishing (METOX 600 only). Switch to DC, use METOX POL 511 polishing solution and apply with the same technique.
8. Marking (optional). Fit the METOX 506 marking carbon, place the METOX 507 marking pad and your custom marking stencil, secure with the METOX 510 O-ring, and use METOX MS 505 marking solution.
9. After work. Clean the brush and accessories with water and store them dry.

For all spare parts and accessories, see the Weld Cleaning Machine — Auxiliary Equipment page.

Differences between grinding, chemical pickling and electrochemical cleaning

Conclusion: chemical pickling suits large-surface series production; electrochemical cleaning suits spot work and on-site repair. Grinding alone is not sufficient where corrosion resistance is required.

Benefits of a weld cleaning machine

Flexibility and ease of use. Portable equipment can be used anywhere and is ideal for on-site repairs. No fixed plant, bath or crane is required.

Application safety. Safe with minimal acid use and appropriate personal protective equipment. Health risks are far lower than with gel cleaners.

Speed. Cleaning and passivation happen simultaneously; a single pass replaces two separate operations, two waiting periods and two rinses.

Optimum corrosion resistance. Passivation provides the best possible corrosion protection on the surface.

Minimum recurring cost. Operating cost is low — only weld cleaning solution (and polishing solution on the METOX 600) plus occasional brush replacement.

Which metals can it be used on?

Weld cleaning and passivation is designed for stainless steels:

Marking works on a far wider range of materials: stainless steel, galvanised steel, chrome steel, carbon steel, aluminium, brass, copper and titanium.

Note on aluminium: aluminium has different surface chemistry from stainless steel. It is suitable for marking, not for weld cleaning. For oxide layers and tarnishing on aluminium surfaces, use METOX AL‑04.