The Letterbox Shop only uses Marine Grade 316 STAINLESS STEEL with an N4 (brushed) finish for all its letterbox face panels and plaques apart from the CORTEN range

Housing boxes will be manufactured with either Marine Grade 316 Stainless Steel or Marine grade 445m2 stainless steel.


Stainless steel is a generic term for a family of corrosion resistant alloy steels containing more than 10.5% chromium. It has excellent weldabilty, formability, fabricability, ductility, cleanability and hygiene characteristics. Good high and excellent low temperature properties. When nickel is added in sufficient amounts the crystalline structure changes to "austenite". Series 300 stainless steels (including G316 and G304) are austenitic and are the most common stainless steels in use in the world today. G316 (also known as UNS S31600, A4 or"316 marine grade" stainless) has molybdenum added for higher corrosion resistance and is recommended for aggressive environments.

For more information on 316 Stainless steel please go to; Australian Stainless Steel Development Corporation (ASSDA)



A brown discolouration commonly known as "tea staining" may also occur, especially in coastal regions. There is no known cause for this and it can occur quite rapidly. It can be controlled by regular maintenance and while it does not cause structural damage it is cosmetically unpleasant. For best cleaning results please use the Stainless steel cleaner and preserver available from The Letter Box Shop or alternate Lanolin based corrosion inhibitors.

Tea Staining can occur with any stainless steel product, which is NOT classed as a defect.

For more information on Tea Staining please go to;

Will the stainless “CORRODE”

The chromium in stainless steel causes a thin film to form on the surface giving stainless its corrosion resistance. When this film is damaged by scratching or surface contamination by foreign materials such as salt, pollution, metal filings etc. corrosion can occur. After removal of rust marks the film self heals after a short period of time.


Weathering steel, best-known under the trademark COR-TEN steel and sometimes written without the hyphen as "Corten steel", is a group of steel alloys which were developed to obviate the need for painting, and form a stable rust-like appearance if exposed to the weather for several years. As you will be able to see from our website, Corten has a rusty finish. Corten is a structural material that was originally designed to be used in shipping containers. The rust creates a protective barrier so the material underneath will not deteriorate over time. There is a big difference between mild steel and Corten. The natural rusted finish on Corten is REAL rust and will leach a stain if exposed to the elements. Please consider this especially if you had planned on having a Lump piece on or near pale coloured walls or tiles.