Stainless steel tools has resistance to atmospheric oxidation, namely rustless property, and resistance to corrosion in medium containing acid, base and salt, that is corrosion resistance. A thin, solid, dense and stable chromium-rich oxidation film (protective film) is formed on the surface of stainless steel. This film prevents further permeate and oxidation of oxygen atom, making the stainless steel of corrosion resistance. Once this film is continuously destroyed for one reason or another, the oxygen atoms in the air or liquid will gradually penetrate into the metal. Then the iron atoms will separate out gradually, forming loose iron oxide. So the metal surface is constantly corroded. The form of such damage to the surface film is various, and the following are the common types in daily life:
1. The surface of stainless steel tools exists dusts of other metals or attachments of dissimilar metal particles. When exposed to humid air, the attachment and stainless steel are connected as a microbattery through the condensate water between them, causing electrochemical reaction. And the protective film is destroyed, called electrochemical corrosion.
2. The stainless steel tool’s surface is attached with organic juices (like fruit, vegetable, noodle soup, phlegm, etc.). In the presence of water, the organic juices oxidize, producing organic acid. The organic acid will corrode the metal surface over the long time.
3. Localized corrosion will occur on stainless steel surface for many a number of reasons, such as the splash of alkaline water and lime water on decorated walls.
4. In the polluted air (such as air containing large quantities of sulfide, carbon oxide and nitrogen oxide), the condensate water is encountered to generate sulfuric acid, hydrogen nitrate and ethylic acid drops. This will lead to chemical corrosion.
All the above conditions can cause damages to the protective film on the surface of stainless steel tools, thus resulting in corrosion. So to ensure that the metal surface is permanently bright and not be corroded, we suggest that:
1. The tools surface must be regularly cleaned and scrubbed to remove the attachments, eliminating the external factors which cause corrosion.
2. To avoid the surface contamination caused by fingerprints, we should wear gloves when using stainless steel tools.
3. Stainless steel tools should be put in clean, dry and well-ventilated places. And we should pay attention to the moisture, dust, oil, lubricant, and surface corrosion or poor welding that may weaken the corrosion resistance.