Cleaning and preservation stainless steel

Vệ sinh và bảo quản Thép không gỉ

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 corrodentsInfluenceEnvironment
1axit HCl, H2SO4Because of the low pH, the passive protective film is unstableBleach, factory, and car exhaust
2Clorit (NaCl, …)Ion Clo dissolves in water to destroy passive protective film.Coastal

Waste treatment area

3Dirty, dust, charcoal sootMix in air, impact on passive protective film.Factory and car exhaust

Near the constructions site

4Difference metalsExposure to metal surfaces occurs self-corrosive metalsThe 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 air

2. The corrosive reaction due to incorrect weld.

3 The corrosion occurs due to weld.

4. Use the wrong cleanser.

Use stainless steel for the right environment.

Stainless steel can maintain longevity and shiny surface by using suitable steel for application environment.

 CountrysideUrbanIndustrial zoneCoastal
 ILMHILMHILMHILMH
Duplex
316
304
430

Pay attention:

  • 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.

 PreventionManagement
Work toolOnly use stainless steel toolsDuring 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.
WeldWelding rodNot mix with other welded rod

Prevents contamination such as moisture, lubricant.

Welds and heat affected areasWhen 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.

otherRemove the protection layerContaminants from the protective layer can create corrosion when placed outdoors, Protective layers are removed after 3-6 months
CleaningWash with water or use detergent neutral to remove oil, soil, dust, iron dust.

 

Cleaning cycles

EnvironmentCountrysideNormal areaCity, industrial zone, coastal
Special area
Areas exposed to rain

(outside)

No pollution1 – 2 times/year2 – 3 times/year3 – 4 times/year
Pollution2 – 3 times/year3 – 4 times/year4 – 5 times/year
Areas not exposed to rain

(outside)

No pollution1 – 2 times/year3 – 4 times/year4 – 5 times/year
Pollution2 – 3 times/year4 – 5 times/year5 – 6 times/year

Cleaning method: wash with water or with neutral detergent.

DustSoap, detergent or dilute 1% ammoniac solution in warm water.

Apply with sponge, soft cloth, soft yarn brush then clean with water and make dry

FingerprintDetergent and warm water or Hydrocacbon solution.
Stain greaseHydrocacbon.
Stain, discoloration, bright spotsUse sponge, soft cloth to wipe with water and dry. Prevent exposure to Clo.
Rust caused by carbon steelAxit Photphoric 10%, then wash by ammoniac and water or axit solution, then wash again with water.
Hard water or cementAxit Photphoric 10%, diluted Amoniac, warm water, neutral, wash with axit and then dry.

Avoid using HCl to remove cement.

DiscolorationAnti- scratch or polish. Use soft or sponge cloth, clean the residue with water and dry

Nylon pads

Stains or dust accumulationUse sandpaper to rub then rinse to remove dirt and iron dust
PaintUsing specialized alkali, solvent depending on the type of paint, using foam, nylon

Cleaning method and remove rust

Rust conditionCleaning method
The first stage of rustNeutral detergent.
Red rustAlthough rust is present, cleaning frequently may return to original state
Rust caused by iron dustIf 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 emissionsThe first stage of the rust, removed by mild detergent. The latter uses 15% nitric acid.
Rust caused saltWindow 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 detergentWash with water

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