Building
Roof or wall washed by rain
Eaves, Soffits or sheltered
areas not washed by rain
Structure
No deposits
Deposits
accumulate
No deposits
Deposits
accumulate
Cleaning in rural, suburban
and residential areas
4/year
6/year
12/year
24/year
Cleaning for seaside,
industrial and severe areas
8/year
12/year
24/year
52/year
Notes:
* cleaning frequency is dependant on surface finish, design details, environment, cleaning procedure and expectations of performance
** cleaning involves using Pro-Railing Enviro-Shield
(189900902)
- which comprises stainless steel cleaner, demineralised water and
protection spray.
Degreasing
Dirt left on the surface after a fabrication process
can have a serious affect on the corrosion
resistance of stainless steel. Not only will it
prevent the steel from oxidizing, it can contain
corrosive particles, which will start rusting at a
later date.
Pickling
Pickling requires the use of strong chemicals
(hydrofluoric acid and nitric acid) to dissolve the
surface of the steel. This process completely
removes any surface contaminants and will help
to restore the chromium level to the weld affected
areas.
The heat from the welding process drives
chromium away from the weld area. The area
adjacent to the weld is often low in chromium and
high in iron. These areas are always the most
susceptible to corrosion once the component is in
use.
Iron dissolves more readily than chromium,
therefore, the pickling process leaves the surface
chromium-rich and in a condition where it can
form a dense oxide layer.
Passivation
Stainless steel will passivate in the open
atmosphere - assuming that it is spotlessly clean
to begin with and so is the air it is sat in. It is a
slow process and, depending on the grade of
stainless, can take between 24-48 hours to occur.
Stainless steel is not self-cleaning!
The chromium-oxide layer that protects stainless
from corrosion is relatively fragile. It can be
broken or damaged during fabrication, if
scratched and/or surface contamination is
allowed to settle on the surface.
The most effective way to form the passive layer
is to force it by subjecting the steel to an oxidizing
chemical. These are typically acid solutions
containing nitric acid or citric acid. This process
speeds up the reaction time and typically takes
around 2-3 hours contact time to fully form a
dense and effective layer.
Simply cleaning a corroded piece of stainless
steel with a stainless steel cleaner and a scouring
pad (usually phosphoric acid or citric acid based)
does not passivate it. These acids will help to
dissolve the corrosion (iron oxides) and leave the
surface in a condition in which it can
self-passivate.
Rain washing regularly will reduce the risk of tea
staining (brown discolouration). This is a visual
impairment only, and does not affect the structural
integrity or longevity of the material. The best way
to prevent it is to follow the cleaning chart below,
but as a general rule of thumb the recommenda-
tion is that the stainless needs cleaning as often
as the glass.
Remember bad design can result in poor
performance e.g. partially sheltered systems will
greatly reduce the benefit of natural washing by
rain. Maintenance of stainless steel should be
considered in the design process.
Recommended cleaning intervals for stainless steel handrail systems
55
CLEANING INTERVALS
