The Lasting Look for Architectural Woven Mesh

You’ve made ‘the lasting decision’ and now for ‘the lasting look’. Cleaning with soap or a mild detergent or even an industrial cleaner is not a realistic approach with fine meshes — as you cannot reach between all the weaves and the tea staining will continue to occur.

What is Tea Staining?

Tea staining is the brown discolouration of the surface of stainless steel caused by corrosion. It is a cosmetic issue that does not affect the structural integrity or life of the stainless steel. Tea staining occurs most commonly within 5km of coastal areas however it can also occur in polluted urban environments.

For further information please refer to The Australian Stainless Steel Development Association (ASSDA) FAQ 6: Preventing Coastal Corrosion (Tea Staining).

Why is Maintenance Necessary?

Surface contamination in the form of deposits must be prevented. These deposits may be minute particles of iron or rust from other sources such as tools previously used on carbon steel. There are also naturally occurring atmospheric conditions which produce deposits, such as salt from marine environments. The more aggressive the environment is, the more regular the cleaning program will be required.

The cleaning frequency of stainless steel depends on four points:

• The environment
• Position of the stainless steel structure
• Stainless steel surface finish and structure design
• Client’s expectations

Cleaning Frequency Guide

A guide to specifying and cleaning external stainless steel:

Source: ASSDA | Note: Rainwater is an effective natural cleaner. Stainless steel that does not get rained upon will need more frequent cleaning.

Electro Polishing & Pickling / Passivation

We have discussed Tea Staining and unfortunately cleaning with soap or a mild detergent or even an industrial cleaner does not suffice with fine meshes — as you cannot reach between all the weaves and the tea staining may return under particular conditions. Where this is an issue is when the mesh is being used for its aesthetic appeal in architectural or external applications.

The solution is pickling & passivation and electro polishing — a simple and inexpensive process that will last the test of time.

Stainless steel can be contaminated by carbon steel which will lead to corrosion. Ideally, a fabricator will have a dedicated workshop and tools for stainless steel only. Contamination can be picked up from:

• Grinding wheels, wire brushes and linishing belts
• Steel storage racks
• Tooling used with other metals
• Contamination from grinding or welding sparks from nearby carbon steel fabrication

It is recommended that when stainless steel is to be used for external purposes that it be electropolished.

Benefits of Electro Polishing

• Remove surface flaws & impurities
• Remove high points and round troughs
• Passivates greater than any other process
• Maximises the protection of stainless steel against tea-staining and corrosion
• Brightens the surface finish to provide a bright and shiny chrome-like appearance
• Smooths the surface enabling the surface to naturally wash, thereby significantly diminishing the likelihood of future rust

Benefits of Pickling & Passivation

• Removes contaminants
• Removes heat tint due to welding
• Formation of a continuous enriched chromium oxide protective layer

For further information please refer to: The Australian Stainless Steel Development Association (ASSDA) — Navigate to technical FAQ’s.