Today, Dai Duong shares for reader how to clean and preserve stainless steel. Stainless steel has more ability resistance corrosion than carbon steel. So, the cleaning and preservation are very essential because the corrosion depends on condition or environment.
The reasons of corrosion of stainless steel
Stainless steel has more ability resistance corrosion than carbon steel. So, the cleaning to and preservation are very essential because the corrosion depends on condition or environment.Stainless steel can be rusted when the protective film is destroyed by some reasons and regeneration of the protective film is interrupted.
- Clo
- The corrosion due to pollution, precipitates and condensates
- The corrosion due to contact with other metals.
- The protective film is destroyed
- Incorrect welding mode and the welded temperature is affected
The corrodents , influence and environment
| No. | The corrodents | Influence | Environment |
| 1 | axit HCl, H2SO4 | Because of the low pH, the passive protective film is unstable | Bleach, factory, and car exhaust |
| 2 | Clorit (NaCl, …) | Ion Clo dissolves in water to destroy passive protective film. | Coastal Waste treatment area |
| 3 | Dirty, dust, charcoal soot | Mix in air, impact on passive protective film. | Factory and car exhaust Near the constructions site |
| 4 | Difference metals | Exposure to metal surfaces occurs self-corrosive metals | The area near the iron steel plant or construction site. |
The corrosion of stainless steel cases
1. The corrosion holes. The passive membranes is destroyed by high Clo content in the air2. The corrosive reaction due to incorrect weld.
3 The corrosion occurs due to weld.
4. Use the wrong cleanser.
- Pls see more how to distinguishing 304 stainless steel at: http://www.inoxdaiduong.com/en/t199/distinguish-304-stainless-steel-with-the-usual-stainless-steel.html
Use stainless steel for the right environment.
Stainless steel can maintain longevity and shiny surface by using suitable steel for application environment.| Countryside | Urban | Industrial zone | Coastal | |||||||||||||
| I | L | M | H | I | L | M | H | I | L | M | H | I | L | M | H | |
| Duplex | ○ | ○ | ○ | ○ | ○ | ○ | ○ | ○ | ○ | ○ | ○ | ○ | ○ | ○ | ○ | ● |
| 316 | ○ | ○ | ○ | ○ | ○ | ○ | ● | ● | ○ | ● | ● | ♦ | ○ | ● | ♦ | ■ |
| 304 | ● | ● | ● | ● | ● | ● | ● | ♦ | ● | ♦ | ♦ | ■ | ● | ♦ | ■ | ■ |
| 430 | ● | ● | ♦ | ♦ | ● | ■ | ■ | ■ | ♦ | ■ | ■ | ■ | ♦ | ■ | ■ | ■ |
- I (Indoor Environment):
- L (Low Grade Environment):
- M (Medium Grade Environment
- H (High Grade Environment)
- ○: very suitable ●: quite suitable ♦: frequently clean ■: Not suitable
Prevention when processing and construction.
| Prevention | Management | |
| Work tool | Only use stainless steel tools | During metal processing will produce dust steel, When using tools for processing carbon steel, dust steel will stick to the surface of the stainless steel, Corrosion may occur due to contact metal. So, only use stainless steel tools or cleaning the tools before using. |
| Weld | Welding rod | Not mix with other welded rod Prevents contamination such as moisture, lubricant. |
| Welds and heat affected areas | When passive protective layer and heat affected area are destroyed by high temperature, need heat treatment to provide resistance to corrosion. Remove the scales at the welding area, using a grinder, brush or sandpaper. Clean welding area to regenerate passive protective layer. | |
| other | Remove the protection layer | Contaminants from the protective layer can create corrosion when placed outdoors, Protective layers are removed after 3-6 months |
| Cleaning | Wash with water or use detergent neutral to remove oil, soil, dust, iron dust. |
Cleaning cycles
| Environment | Countryside | Normal area | City, industrial zone, coastal | |
| Special area | ||||
| Areas exposed to rain (outside) | No pollution | 1 – 2 times/year | 2 – 3 times/year | 3 – 4 times/year |
| Pollution | 2 – 3 times/year | 3 – 4 times/year | 4 – 5 times/year | |
| Areas not exposed to rain (outside) | No pollution | 1 – 2 times/year | 3 – 4 times/year | 4 – 5 times/year |
| Pollution | 2 – 3 times/year | 4 – 5 times/year | 5 – 6 times/year | |
| Cleaning method | |
| Dust | Soap, detergent or dilute 1% ammoniac solution in warm water. Apply with sponge, soft cloth, soft yarn brush then clean with water and make dry |
| Fingerprint | Detergent and warm water or Hydrocacbon solution. |
| Stain grease | Hydrocacbon. |
| Stain, discoloration, bright spots | Use sponge, soft cloth to wipe with water and dry. Prevent exposure to Clo. |
| Rust caused by carbon steel | Axit Photphoric 10%, then wash by ammoniac and water or axit solution, then wash again with water. |
| Hard water or cement | Axit Photphoric 10%, diluted Amoniac, warm water, neutral, wash with axit and then dry. Avoid using HCl to remove cement. |
| Discoloration | Anti- scratch or polish. Use soft or sponge cloth, clean the residue with water and dry Nylon pads |
| Stains or dust accumulation | Use sandpaper to rub then rinse to remove dirt and iron dust |
| Paint | Using specialized alkali, solvent depending on the type of paint, using foam, nylon |
Cleaning method and remove rust
| Rust condition | Cleaning method |
| The first stage of rust | Neutral detergent. |
| Red rust | Although rust is present, cleaning frequently may return to original state |
| Rust caused by iron dust | If rust can not be removed by normal detergent, remove rust by sandpaper or brush made of stainless steel. The first stage of rust, the rust is removed by mild detergent. The latter use 15% nitric acid. |
| Rust caused by acid rain or emissions | The first stage of the rust, removed by mild detergent. The latter uses 15% nitric acid. |
| Rust caused salt | Window frames or balustrades in coastal areas can cause red rust in a short time. Use special paint for stainless steel or regular cleaning. |
| Rust caused by detergent | Wash with water |
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