What is Tea Staining
Tea Staining is a brown discolouration that has been identified in coastal applications in Australia and overseas. Often, this occurs through mishandling of the wire, incorrect specification, fabrication or installation in coastal environments. The result is that stainless steel posts or wire may stain or discolour, impairing the overall look. However, it does not affect the structural integrity or the longevity of the material.
Uncontrolled tea staining worsens the closer the wire installation is to the marine source. It is mostly restricted to within about five kilometres of the beachfront, or a few hundred meters from a sheltered bay and rarely occurs inland. Other environmental factors may contribute to the problem such as wind exposure, industrial pollution, and elevated temperatures where tea staining may occur up to 20 kilometres from the sea.
A rough surface finish promotes tea staining – e.g. satin finish posts or rails and 7×7 or 7×19 structured wire. The main cause of this problem is salt deposited on the stainless steel surface. The smoother the surface the better. Simply choose the smoothest shiniest surface you can to reduce the risk of tea staining. Smoother surface finishes stay cleaner between washes and don´t have deep surface grooves where chlorides and other contaminates can collect and concentrate.
Prevention of Tea Stains
Always use AISI Grade 316 in all marine and highly corrosive environments – and then care for it. Even smooth stainless steel finishes in coastal environments may show tea staining if not washed regularly. Even simple rain washing the stainless steel surface can help reduce tea staining, and should therefore be an important project design consideration.
Best Results are achieved by washing with soap or mild detergent and warm water followed by rinsing with clean cold water. Surface appearance may be further improved by wiping dry the washed surface and treating the stainless steel with protective materials (e.g. Lanotec).
Regular maintenance and use of lanolin protective products will ensure the best resistance against tea staining and corrosive effects. As well, a process called picking may be used to remove surface contaminants, but may dull the surface. Alternately electro polishing may be sued, and has the added benefit of brightening the surface.