What is needed for a STAINLESS STEEL surface?
* A smooth surface so contaminants are not
trapped or allowed to concentrate.
* A surface free of dirt and grease so the
chromium oxide has air access.
* A thick, continuous chromium oxide film.
• PRE-Welding surface preparation can improve
the amount of contaminants produced during
• Welding itself is not generally the problem.
• The issue is pre and post-weld cleaning…….
• - Minimize preparation contaminants
- Remove heat tint
- Remove layer with lower Cr
Metal cutting fluids.
Shared metal cutting / grinding equipment.
Remove weld heat tint and scale.
Remove embedded iron.
Remove light surface iron contamination.
Immediately forms the protective oxide film.
Enrich the surface with chromium .
• Pickling acids remove heavy weld scale, heat
tint, the depleted chromium layer.
HF based pickling agents attack stainless.
PICKLE PASTE is a OH&S issue.
Hydrofluoric acid is a schedule 7 poison.
• Steels containing more than 11%
Chromium are capable of forming an
invisible, inert or passive, self-repairing
oxide film on their surface.
• It is this passive layer that gives
stainless steels their corrosion
To render a metal less liable to corrosion by
coating the surface with a substance, such as
Passivation also is accomplished by ...................
The passivation of stainless steel is
performed when free iron, welding
scale, welding tint, iron particles
are removed from the surface to
allow the protective oxide layer to
Increases the Chromium content of
is a electrochemical process that is a......
of stainless steel and results in a
more passive surface.
This is typically done to remove any "free-
iron" from the surface of the metal, which
enhances the corrosion resistance of the
stainless steel surface and accelerates
the re-formation of the passive layer.
The electropolishing process smoothes
and streamlines the microscopic
surface of a metal object.
As a result, the surface of the
metal is microscopically featureless.
ie. a brighter surface.
decreased by 25 to 35%.
Courtesy of MME Surface Finishing
high points or "peaks"
much faster than the
corresponding rate of
attack on the
Smoothness of the metal surface is
a very advantageous effect of
During the process, a film of varying
thickness covers the surfaces of the
a valuable alternative.....
To Pickling paste
( Hf + Nitric )
Nitric acid for Passivating
Can electropolishing improve
corrosion resistance ?
Surface is smoothed and polished.
Sharp edges are removed.
Burrs are removed.
Embedded iron particles are removed.
A Completely passivated surface is
Darling Harbour , Sydney
A summary in a picture...
316 handrails at
Tea stained – No4 finish,
Not tea stained – pickled No4
near the weld, treated when
the weld was pickled.
Not tea stained – a high polish finish .
Stained – the weld was not
pickled well enough, there was
low chromium layer left in the
Ra.......measure of surface roughness
STAINLESS FUME HOOD with CARBON STEEL clamping rings.
PRE and POST CLEANING stages using the GWC SYSTEM.
CARBON FIBRE BRUSH RANGE
WIDE BRUSH RANGE
50 mm WIDE SMALL
100 mm WIDE SMALL
30 mm WIDE MEDIUM
50 mm WIDE MEDIUM
50 mm WIDE LARGE
100 mm WIDE LARGE
ROUND BRUSH RANGE
SMALL ‘O’ RING
MEDIUM ‘O’ RING
LARGE ‘O’ RING
30 mm ROUND
For best results a supply of clean, ripple-free DC
power must be available to drive the process.
The DC power must be applied at the correct
voltage and current for best results.
WELD POSTCLEENER specifications.
THE WELD POSTCLEEN SYSTEM
HOW the WP – WELD POSTCLEEN can help you.
1/ FAST EFFICIENT CLEANING AND ELECTROPOLISHING OF
STAINLESS STEEL PRODUCTS WITH THE HIGH POWER OF SYSTEMS AVAILABLE.
2/ NO MORE USING DANGEROUS TOXIC PICKLE PASTE AND NITRIC
ACID CHEMICALS THAT ARE ENVIROMENTIALLY HAZARDOUS
AND A MAJOR OH&S ISSUE.
3/ MOST POWERFUL SMALL PORTABLE SYSTEM ON THE
4/ POWER SUPPLIES FULLY ADJUSTABLE FROM 100 watts TO 1000
watts WITH SINGLE SYSTEMS.
200 watts TO 2000 watts WITH THE DUAL SYSTEM.
5/ DUAL SYSTEM CAN BE SPLIT TO OPERATE AS TWO ISOLATED SYSTEMS.
6/ CLEAN INTO THE TIGHT CORNERS OF STRUCTURES WITH THE WIDE
RANGE OF FLEXIBLE BRUSHES.
7/ EASY REMOVAL OF TEA-STAINING.
8/ LARGE SURFACE AREA CLEANING / PASSIVATING OR
POLISHING WITH THE LARGER BRUSH SIZES AVAILABLE.
9/ PORTABLE FOR ONSITE WORK.
10/ EXTEND THE RANGE OF ELECTROPOLISHING BY USING THE
ADVANCED DESIGNED BRUSHES.
11/ POWER SUPPLY VERY RELIABLE.............100% DUTY CYCLE.