Care and use in shop

Contamination

The number ONE problem with unsuccessful fabrication of stainless steel is “contamination.”  Ideally, the shop should have a separate area where ONLY stainless steel is fabricated. This will prevent the contamination of the stainless steel surface with “iron” particles that are picked up from the surface of the fabrication machinery when previously used to fabricate carbon steel.   If one has to use the same equipment to process both carbon and stainless steel, a thorough “cleaning” of the machinery is required before processing stainless. These tiny carbon steel particles will be embedded in the surface of the stainless steel and will, over time, begin to rust, so it will appear that the stainless steel is “rusting.”

Other ways of contamination the surface of the stainless steel is to use a “wire” brush that is made of carbon steel to clean the surface or to clean off welding scale.  Only nonmetallic (or stainless steel) material should be used in cleaning the surface. Likewise, do not use steel wool or grinding wheels that have been previous used to grind carbon steel.

Handling

Mechanical damage (e.g., scratches and gouges) can occur easily during handling if not guarded against. Such mechanical damage will result in the passive oxide film being “punctured” leading to a possible lower resistance to the initiation of corrosion than the surrounding chemically passivated surface. In addition, corrosion in such areas can be accelerated by the galvanic corrosion effect due to the unfavorable relative area ratios which exist.

• Plates and sheets should be stored vertically in racks and not be dragged out of the racks or over one another. Racks should be protected to prevent iron contamination.
• Heavy plates should be carefully separated and chocked with wooden blocks, in order for the forks of a fork-lift to be inserted between plates without mechanically damaging the surface. If the forks are haphazardly forced in between plates, some degree of contamination of the scratches and gouges could also occur, thus aggravating the damage so induced.
• Plates and sheets laid out for use should be off the floor and be divided by wooden planks to prevent surface damage and facilitate subsequent handling.
• Plate clamps, if used, must be used with care as the serrated faces usually dig in, indent and gouge the surface.
• If chain slings are used, these inevitably tend to slip, again causing mechanical damage of the surface. Slings of heavy-duty synthetic material are preferable.
• Thin gauge cold rolled material often has a superior finish (e.g., polished or bright annealed). Clean linen gloves should be worn when handling such material to avoid finger markings. Such marks can be removed by the use of a mild organic solvent followed by cleaning with a warm detergent solution. Sometimes a warm detergent will suffice. Thorough clean water rinsing and drying complete the removal procedure.

Note: ASTM A380 describes a number of ways fabricating shops can reduce surface contamination during fabrication.

Cleaning

The cleaner stainless steel can be kept while in storage, being processed or during use, the greater the assurance of optimum corrosion resistance. Some tips on the care of stainless steel are listed below:

1. Use paper or other protective wrapping on the surface of the stainless steel until processing is complete.*
2. Handle stainless steel with clean gloves or cloths to guard against stains or finger marks.
3. Avoid the use of oily rags or greasy cloths when wiping the surface.
4. Do routine cleaning of exposed surfaces. Buildings with window washing systems can utilize this method to clean exterior panels.
5. Where possible, after cleaning, rinse thoroughly with water.
6. Cleaning with chloride-containing detergents must be avoided.
7. Even the finest cleaning powders can scratch or burnish a mill-rolled finish.
8. On polished finishes, rubbing or wiping should be done in the direction of the polish lines, NOT across them.
9. DO NOT USE SOLVENTS in closed spaces or while smoking.

*Many adhesive-backed papers and plastic sheets or tape applied to stainless steel for protection “age” in fairly short periods of time and become extremely difficult to remove. Manufacturers should be contacted regarding information as to how long protective films or paper can be left in place.