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How does mgo board corrode steel ?

Views:383     Author:Site Editor     Publish Time: 2016-06-28      Origin:Site

Magnesium oxide board,"mgo board" in short,it is kind of artificial crystal,synthesize by "oxide"-magnesium oxide + "salt"-magnesium chloride and water.The chemical reaction was 1st discovered by French-Dr.Sirel in 1867,In 1980's Chinese started to use this technical to made fire resistant wall board.The panel is green product with extreme good physical performance,it became popular quite soon.However in recent years,there are many complaint about mgo board defect on internet,such as


-screws and frame affect by chloride ions and get rust
-the wall get damp in rainy days and plaster drop
-panel get powery after soak and dry
-bend or crack at the joint after few months

The quality level of mgo board depend on production management and chemical technical(formula)

The fundamental cause of defect such as chloride ions release and moisture damage is from

one reaction raw material - magnesium chloride

Other defects such as flatness,bubble,edge un-square that can be avoid by QC.

Today we are talking about the fetal flaw of mgo board, chloride content in mgo board,about 8%-15%


What is Cl- Corrosion?

Metallic corrosion is the process of either stealing or donating electrons, when the electrons are stolen or donated, the metal atoms will dissolve in the water. Salt water is a the main conductor, so the rate of corrosion increases dramatically. When mgo board in high humidty enviroment,8-15%

free chloride iron will dissolve and move toward water,when it contact with metal,unavoidale corrosion will happen on its surface. 


The effects of oxidation on metals such as mild steel are obvious and the destruction is rapid. Metals such as stainless steel, titanium, manganese bronze and anodised aluminium minimise this destruction by forming a thin, protective oxide layer covering their surface.When salt is present, the chloride (Cl-) ions attack this oxidised layer, penetrating and exposing fresh aluminium. This then corrodes only to be stripped off again in a never ending cycle. So the natural protection Aluminium gets from an oxide coating is useless against salt! 


The chloride (negatively charged ion) Cl and minus. It is formed when the element chlorine (a halogen) gains an electron or when a compound such as hydrogen chloride is dissolved in water or other polar solvents.  Before magnesium oxide mix with magnesium chloride,the magnesium chloride have to dissolved in water as solvent,to make sure all the oxide material entirely react with salt next to impossible in real production,thus there will be some salt does not participate in the reaction which is going to weak up in near future.


Let's see some examples:

There is one of mgo board fasten by dacro treament screw,we put in interior-high humidity place,

only after 6 month,all the screw get rust and there are plenty of powder on its surface.
IMG_3957 IMG_3956


Magnesium oxide board 15mm-18mm has been widely use as ventlating duct in China,

Generally the surface of mgo duct painted with acrylic emulsion as photoes.
ventlate duct made of mgo
IMG_4394
screw piont

1,The surface get damp badly. It will speed up process of plaster slip and chalk.

2,All the contacted metal-galvanized frame or screw will rust in shortly

Steel pipe does not rust,please note they are in the same enviorment

3,Screw entirely damaged and change shape.


Not all the mgo boards are the same.


RockMax Magnesium Cement Board is a new generation formula product

which does not contain chloride,chloride ion close to 0%,tested under ASTM C871

water absorbtion rate < 10%  24 hours in normal condition,ASTM C 473

bend strength of 12mm >16MPA   9mm > 19 Mpa


Consider about the above fact,I appeal all the mgo board distributors and end user stop use 

mgo board(contains chloride) in steel frame system or other building elements.

Chloride mgo board will corrode your benefit and reputation forever!


                                                                                              Wrote by Mr Franklin
                                                                                          Magnesium Cement Technican 
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