Cleaning Stainless Steel Foot Grilles

“Iron residue on the surfaces of Stainless steel parts (either cast or wrought) has been a recurring problem for many years  --  probably since Stainless steels were first developed.  Here we will discuss the possible sources of the residue, the consequences of it being present, methods for detecting it, and methods for removing it. 

First, a word about what iron residue is and what it is not.  The residue is free (unalloyed) iron on the surface.  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. © 2005)

What are the Sources of Free Iron?  Too many to list but the most potential problems/exposure for Stainless Steel Gridline would include:

            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).

What are the Consequences of Free Iron Exposure and how does this effect GridLine Grids?  Some general categories include:

            Appearance:  Free Iron on any surface can rust.  The appearance of rust is seen as deterioration and is objectionable. 

            Material Identification:  Rust is associated with and therefore assumed to be iron or steel parts.

            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. 

Free Iron does not cause pitting corrosion, etc. 

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, the water will accelerate the reaction of the surface free iron with oxygen and form readily visible iron oxide (rust).  You can also use a copper sulfate spray or the “ferroxyl test.”

REMOVING FREE IRON CONTAMINATION FROM GRIDLINE G6 ENTRANCE GRID.

Mechanical removal methods will not work  --  abrasive blasting merely moves the iron around on the surface.  The only mechanical methods which are successful are machining or grinding which remove the surface.

Not all chemical methods are appropriate or successful at removing free iron from Gridline G6 Entrance Grids.   Oxidation, pickling or electropolishing are not available/appropriate for use on this surface size.

Chemical Cleaning  --  some citrus-based cleaners have been shown to remove free iron contamination.  

Summary:

“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 electrolchemical methods; abrasive blasting alone is not effective.”  (Stainless Foundry & Engineering, Inc. © 2005)