Welding and hot working leave stainless steel with a dark oxide scale and a heat tint around every joint. Under that layer the surface is depleted in chromium and corrodes sooner than the parent metal. Pickling removes the layer: the fabrication is treated with a controlled acid solution, by immersion or by paste and spray, then thoroughly rinsed. What remains is clean stainless steel with its full corrosion resistance restored across the whole surface, welds included.
What gets pickled
- Welded tanks, vessels, hoppers and frames in stainless steel before they go into service.
- Process piping and spools, inside and out, for food, pharmaceutical and chemical plants.
- Architectural fabrications — screens, frames and posts — before polishing or bead finishing.
- Hot-formed and heat-treated parts carrying mill scale.
Why pickle a stainless steel fabrication
Stainless steel resists corrosion because of a thin chromium-oxide film. Welding destroys that film locally and leaves scale, heat tint and sometimes iron particles from tools and grinding. Left alone, those areas rust first, and a stainless tank that shows brown streaks at every weld is a fabrication that was not pickled. Pickling takes the damaged layer off chemically, evenly, including inside corners and weld roots a grinder cannot reach, and the passive film re-forms on the clean metal.
Pickling is followed by passivation where the specification asks for it, and by polishing or bead finishing where the surface is seen.
From your fabrication to a clean surface
- Send the fabrication or the drawing with the material grade and the surfaces to be treated.
- We confirm the method — immersion for parts that fit the bath, paste or spray for large and site-assembled work — and any masking.
- The fabrication is degreased, pickled, rinsed and dried, then inspected for uniform colour and the absence of tint.
- Work continues to passivation, polishing or bead finishing, or is packed and protected for delivery.