Cleaning and preservation stainless steel 2018

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 air
2. 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

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○

○

○

○

○

○

○

○

○

○

○

○

○

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316

○

○

○

○

○

○

●

●

○

●

●

♦

○

●

♦

■

304

●

●

●

●

●

●

●

♦

●

♦

♦

■

●

♦

■

■

430

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●

♦

♦

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■

■

■

♦

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■

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♦

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■

■

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.

	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: wash with water or with neutral detergent.

	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

Stainless steel - Dai Duong
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