1. Dust
Production is often carried out in dusty venues, and there are often many dusts in the air, which are constantly falling on the surface of the equipment. They can be removed with water or alkaline solution. However, adhesion of dirt requires high-pressure water or steam to clean up.
2. Floating iron powder or embedded iron
On any surface, free iron will rust and cause corrosion of stainless steel. Therefore, it must be cleared. Floating powder can generally be removed with the dust. Some have strong adhesion and must be treated with embedded iron. In addition to dust, there are many sources of surface iron, including cleaning with ordinary carbon steel wire brushes and shot blasting with sand, glass beads or other abrasives that have been used on plain carbon steel, low alloy steel or cast iron parts, or Grind the aforementioned non-stainless steel products near stainless steel parts and equipment. In the process of unloading or hoisting, if no protective measures are taken for stainless steel, the steel wire rope, spreader and the iron on the work surface are easy to embed or contaminate the surface.
Ordering requirements and inspection after production can prevent and find the existence of free iron. ASTM Standard A380 [3] specifies the rust test method for inspecting iron or steel particles on the surface of stainless steel. This test method should be used when it is required that iron must not be present. If the result is satisfactory, use clean pure water or nitric acid to wash the surface until the dark blue color disappears completely.
As the standard A380 [3] pointed out, if the rust test solution cannot be completely removed, it is not recommended to use this test method on the process surface of the equipment, that is, the direct contact surface used to produce human consumer products. A simpler test method is to expose for 12 to 24 hours in water to check for rust spots. This test is poorly sensitive and time-consuming. These are inspection tests, not cleanup methods. If iron is found, it must be cleaned up with the chemical and electrochemical methods described later.
3. Scratches
In order to prevent the accumulation of process lubricants or products and/or dirt, scratches and other rough surfaces must be mechanically cleaned.
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