Advantages offered by electrochemical weld cleaning as explained by Mr. Keyur Sanghvi, Managing Partner,
Mehta Sanghvi & Co.
WHAT IS PICKLING AND PASSIVATION?
Pickling is the removal of any high temperature scale, Oxidation, Heat affected zone and any adjacent
low chromium layer of metal from the surface of stainless steel.
Passivation is the treatment of the surface of stainless steels to remove contaminants and promote the
formation of the passive film on a stainless steel surface. (Chromium oxide layer to prevent is from
corrosion)
WHY IS PICKLING AND PASSIVATION NEEDED?
Where the steel has been heated by welding, heat treatments or other means, to the point where a
coloured oxide layer can be seen, there is a chromium depleted layer on the surface of the steel
underneath the oxide layer. The lower chromium content gives lower corrosion resistance. To restore
the best corrosion resistant performance, the damaged metal layer must be removed & this can be
achieved with one of the latest technology of electrochemical stainless steel weld cleaning
machines.
THIS IS WHAT THE LATEST TECHNOLOGY OFFERS:
• Electrochemical/electrolytic weld cleaning machines are the latest trend in weld cleaning
process with assurance of a safer, quicker and better alternative to conventional pickling.
• A rising concern on health and safety has made stainless steel fabricators look for alternative
stainless steel weld cleaners to make the aggressive pickling paste a thing of the past.
• The method: The treatment, based on an electrochemical principle, uses specific electrolytes
and patented electrodes: the advantage is to increase the corrosion resistance, working speed
(instant process) and surface appearance on stainless steel, avoiding the traditional pickling
solutions (which usually contain high concentrations of strong and toxic acids).
• It uses an automatic pump for dosing the liquid; saves water; environment friendly weld
cleaning methods no use of water to rinse the hazardous chemicals in environment; polishing
to improve the aesthetics.; very easy and safer neutralization/passivation; marking/engraving
of logos, barcodes, product names and numbers, No formation of oxide on the surface in
future.
• The research methodology: (Carried out by Nitty Gritty Srl. Italy) Different solutions were
prepared using low concentrations of weak organic acids, to obtain a neutral solution used to
clean/gain high passivation on stainless steel surfaces. This aspect is very important to reduce
the hazardousness of the solution compared to the pure phosphoric acid (standard solution) and
moreover to the traditional pickling acids.
• The best solutions in terms of aesthetic result were tested in terms of corrosion resistance XPS
analysis, on TIG and MIG samples.
• A S.E.M. analysis is used to show the influence of the carbon fibre effect depending on the
technology used (transformer vs inverter) and electrolyte. Several real field applications is
presented. The aim of the second work is to study the electrochemical marking process that
allows to obtain technical and decorative graphical effects on stainless steel by the controlled
growth of protective oxides and to develop new electrolytes able to increase even more the
technical and aesthetic result on different stainless steels series.
