GRADES: There are many grades of Stainless Steel, the majority of stainless steel items are either grade 304, 316 or 316L, which are members of the Austentic family.
GRADE 304: Has good corrosion resistance and is one of the most commonly used grades of stainless steel.
GRADE 316: Has a higher level of corrosion resistance. The grade 316 is often referred to as “marine grade”. Typical applications are boat fittings and architectural components for exposed coastal applications. The majority of products in this catalogue are grade 316.
GRADE 316L: Has similar properties to grade 316. The “L” stands for lower carbon content.
What is tea staining?
Tea staining can be defined as: discolouration of the surface of stainless steel that does not affect the structural integrity or the longevity of the material.
Contributing factors.....And what can be done about them.
The relationships between the contributing factors are complex, but generally become increasingly critical closer to marine water.
Tea staining occurs most commonly within about 5 kilometres from the surf and becomes progressively worse closer to the marine source. However, wind exposure, pollution levels and higher temperatures can create environments where tea staining might occur 20 kilometres or more from the sea water. These same factors also increase corrosion rates of alternative materials.
Rough surface finishes promote tea staining: The smoother the surface finish, the better. A surface roughness (Ra) of less than .05 micrometres is strongly recommended, a No: 4 finish is inadequate. Typically the products are 320 grit or higher which achieves a finish better than 0.5 micrometres Ra.
Stainless Steel is not maintenance free but maintenance friendly. When using stainless steel material outdoors you need to clean periodically, especially in aggressive environments like coastal areas or swimming pools. Washing regularly will reduce the risk of tea staining. For best results wash with soap or mild detergent and warm water, followed by rinsing with cold water. The appearance of the surface can be improved further if the washed surface is wiped dry. There are a few products in this catalogue we recommend for maintenance and cleaning.
Installation and inspection.
After installation the completed structure should be washed and inspected for imperfections or contaminants caused by the installation process. If discovered, imperfections should be cleaned off and polished with a suitable stainless polish. Hydrochloric acid, sometimes used to clean cement or mortar residues, should NOT be used on stainless steel as it will stain the surface and may start more serious corrosion.