Why does my Stainless Steel have an Unsightly Brown Discolouration?

Don’t panic this is known as “tea staining”, a common cause of the deterioration of stainless steel surfaces. This is the unsightly brown discolouration caused by corrosion. While it is a cosmetic issue only, and does not affect the structural integrity or lifetime of the material, it makes the appearance of initially pristine stainless steel, very unattractive.

Stainless steel is used in applications that require good visual appeal and structural integrity in a wide range of environments. With minimal care, your stainless steel wire or mesh product will continue to look good for many, many years. However, stainless steel is “LOW maintenance”, not “NO maintenance”.

Stainless Steel Tea Staining Discolouration
Stainless Steel Discolouration known as Tea Staining

 

Major Cause of Tea Staining
The presence of sea salt on the surface of stainless steel is the major cause. Sea salt stays “wet” (and corrosive) until a very low relative humidity. Tea staining also occurs in polluted urban environments.

Tea staining generally does not occur indoors because of the clean environment and low humidity.

Stainless Steel selection- Grade 304 or 316?
We offer grade 304 and 316. As a general rule, grade 316 should be selected for applications within 5km of a surf coast, or 1km from sheltered coastal waters, however, tea staining can occur up to 20km from the coast, depending on environmental factors.

Factors that can increase tea staining are

  • High temperatures and high relative humidity, as found in tropical areas. The moisture in the air dissolves the salt deposits on the surface and keeps them wet
  • Rain sheltered areas, such as the under side of a sloping roof or a building rain shadow
  • Poor drainage or designs with corners, grooves, folds and crevices which can trap water. These can lead to more serious corrosion than tea staining

Fabricating with Stainless Steel
When fabricating with stainless steel wire or mesh, be aware that other causes of staining that are not “tea staining”, include carbon steel contamination, uncleaned welds and chemical fumes, such as hydrochloric acid or bleach.

Prevention, Minimising & Maintenance
Tea staining can be prevented or minimised, firstly by selecting a 316 grade product, and then by regular washing of stainless steel surfaces. An ideal wash is a warm soapy water wash, followed by a fresh water rinse and dry, but if this is impractical, conduct a high pressure, fresh water wash.

Recommended washing frequency is:

Distance from Coast Cleaning Interval
Less than 500m 2 to 4 times per month
500m to 1 km Once a month
1km to 10km Every 4 months
More than 10km Every 6 months

The washing frequency may be reduced for surfaces subject to regular flushing by natural rainfall.

Or keeping it simple when you wash your windows wash your stainless steel!

For further information have a look at our care page
http://www.sswm.com.au/Care

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