Stainless steel was first invented by Harry Brearley in 1913, when a small amount of chromium was added to iron creating a metal that was resistant to both corrosion and rust. Brearley discovered this metal when he was working to identify a solution to the erosion problem seen in the gun barrels of the British Army (Great Plains Stainless). Since its discovery, stainless steel was put together in a wide range of functions and applications including stainless steel entrance grilles.
Stainless steel is resistant to rusting and other forms of deterioration. During your grids lifetime it might be exposed to other elements that can cosmetically alter the appearance. Iron residue on the surfaces of stainless-steel parts (either cast or wrought) has been a recurring problem since stainless steels were first developed. Below are some steps for maintaining the pristine appearance of your stainless-steel foot grille, but before we can get to that we are going to do a deeper dive of free iron.
Sources of Iron Residue
Iron residue is free (Unalloyed) iron on the surface of stainless steel. “Free iron should not be confused with Alloyed iron, which is a major component of the Stainless steel, or with ferrite which is a specific type of crystalline structure and a normal component of Stainless steel, especially cast Stainless steel.” (Stainless Foundry & Engineering, Inc.)
There are a lot of sources of Free Iron, but some of the most common problems/ exposure for Stainless Steel GridLine Grids are:
Tools – hammers, wrenches, pliers, etc.
The atmosphere -- air contains a surprising amount of iron
Water -- water used for cleaning or water brought in the building. Water contains other chemicals which might leave rust-colored spots (do not mistake these spots with free iron).
Consequences of Free Iron Exposure
Free Iron Exposure can affect GridLine Grids is several ways:
Appearance: Free Iron on any surface can rust. The appearance of rust is seen as deterioration and is objectionable.
Material Identification: Rust is common in iron and steel parts; the appearance of rust can lead to incorrect material identification and misassumptions about the product.
Process Contamination: When exposed to pure substances (certain chemicals, etc.) even small amounts of iron can change the color or performance of Stainless Steel parts or GridLine grids.
Note: Free Iron does not cause pitting corrosion, etc.
Methods for Detecting Iron Residue
How to Identify Free Iron on a Stainless Steel GridLine G6 Entrance Mat. Free iron is invisible on the surface. There are several methods used to identify free iron on a stainless steel surface. By simply moistening the surface with clean water, by either spraying or immersing with clean water, the water will accelerate the reaction of the surface free iron with oxygen and form readily visible iron oxide (rust). *Note: If using this method, it is very important that the water is clean. If it contains iron (from iron plumbing) or certain other chemicals, it will give you a false identifier of iron on the surface. You can also use a copper sulfate test or the ferroxyl test to identify the presence of iron for immediate results.
Techniques for Removing Iron Contamination
Removing free iron contamination from GridLine G6 Entrance Grids
· Chemical Cleaning- some cleaning solutions can be used to clean and re-passivate or purify the metal surface and create a protective coating.
Stainless steel cleaners such as Shelia Shine or Simple Green will help to maintain surface shine when used periodically.
Some citrus based cleaners like Citrisurf 2310 or similar chemicals to clean and re-passivate the material and prevent corrosion. Follow manufacturer instructions.
Note: Not all chemical methods are suitable or successful at removing free iron from GridLineG6 Entrance Grids. Oxidation, pickling or electropolishing are not acceptable for use on this surface size.
· Mechanical Cleaning- The only mechanical methods which are successful for stainless steel grids are machining or grinding which removes the surface of the stainless steel
Most mechanical removal methods will not work to remove free iron from stainless steel -- abrasive blasting simply moves the iron around on the surface.
“Contamination of Stainless steel surfaces with free iron is common. It can be avoided only with very careful handling. The presence of free iron on the surfaces of interest can be detected by a variety of tests, including the copper sulfate and ferroxyl tests. Iron contamination can be removed by certain chemical or electro-chemical methods; abrasive blasting alone is not effective.” (Stainless Foundry & Engineering, Inc.)
With proper care and maintenance your stainless steel grille will uphold its sleek appearance and free iron won’t be a concern for your GridLine Grid.
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