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電位差腐蝕解決方案

電位差腐蝕解決方案

異金屬腐蝕

兩種不同的金屬接觸時

電位較低的會先開始腐蝕

電位差距越大反應的越快速

加速腐蝕因素

足量的水、氧氣、離子

陽極面積小、陰極面積大

高氣壓、高溫度環境

金屬,因為產量豐富且易加工的特性,使其不論在建築、橋梁、造船等皆有所使用,是目前應用最為廣泛的材料之一。然而,也因其特性,只要暴露在空氣中就會有氧化反應,部分氧化反應會導致金屬損壞,而最易被忽略的便是「異金屬腐蝕」的狀況,若是不建立正確觀念,便容易引發不可預期的災難。

「電位差腐蝕」是什麼?

金屬之氧化,其實是一種自然現象,任何物質皆會有此現象,若是發生在鐵元素就會有生鏽的情況;若是表現在銅元素則會在外層產生綠鏽……,每種金屬反應皆不同。有些金屬本質不會被影響,有些金屬卻會被腐蝕,導致無法挽回的毀壞。

導致金屬腐蝕的原因主要有三種:化學腐蝕、電化學腐蝕及生物腐蝕。其中又以「電化學腐蝕」最為常見,即我們一般熟知的氧化反應,也就是金屬本身與空氣中的水和氧反應,最後失去電子、留下氧化物的過程。

 

為什麼金屬會失去電子?正是因其「標準還原電位差」低於氧氣,所以電子會被電位高的氧氣搶走,導致結構受到破壞、影響原有特性。而這種因電位差而造成腐蝕的現象,我們就稱之為「電位差腐蝕」

兩種異金屬造成的腐蝕現象

但鮮少人知道的是,當兩種不同金屬放在一起時,其實也會加速腐蝕。例如窗框與鎖扣若採用不同金屬,便容易導致接觸面腐蝕的狀況。

 

異金屬接合之所以會加速腐蝕,正是因為不同的金屬,如:鐵、鋁、鋼、銅等,具有不同的「電位」,也就如同鐵的電位低於氧氣,所以會引發生鏽一樣。

 

兩種金屬之間也存在電位差,所以會導致電位低的金屬加速腐蝕,反之,電位高的金屬則會受到保護,例如:銅的標準還原電位差0.34 volts,鐵則是- 0.44 volts,當兩者相接時,鐵會加速腐蝕。

雖然局部腐蝕的問題並不會造成金屬材料的大量損耗,但會因為不易察覺,而造成突發性的破壞,甚至產生不可預期的災難,例如管線若採用不同金屬材質,就可能出現局部穿孔,導致氣體外泄、液體外流的情況,嚴重可能引發火災或爆炸等情況。

 

因此,金屬電位差腐蝕的問題不能只單看表面,而是必須建立正確的觀念,並且徹底預防,在有異金屬接合的地方都必須加以隔離,尤其是建築外吊掛或固定件,否則因腐蝕而造成的損耗將不僅限於材料與金錢,而是會發生無法彌補的傷害。


聚塑新材料公司能提供金屬電位差
腐蝕的有效解決方案有效率且經過政府機構合格採用

www.dwh.com.tw


 

Potential difference corrosion solution

Heterometallic corrosion

• When two different metals are in contact

• Lower potential will begin to corrode first

• The greater the potential difference, the faster the response


Accelerated corrosion factor

• A sufficient amount of water, oxygen, ions

• Small anode area and large cathode area

• High pressure, high temperature environment

Metal, because of its abundant production and easy processing, makes it one of the most widely used materials in construction, bridges, shipbuilding, etc. However, due to its characteristics, as long as it is exposed to the air, there will be an oxidation reaction, and partial oxidation will cause metal damage. The most easily overlooked is the "isometallic corrosion" condition. If it is not established, it is easy. Cause an unexpected disaster.


What is "potential corrosion"?

The oxidation of metal is actually a natural phenomenon. Any kind of material will have this phenomenon. If it occurs in iron, it will rust. If it is expressed in copper, it will produce green rust in the outer layer.... All are different. Some metals are not affected in nature, and some metals are corroded, causing irreparable damage.

There are three main causes of metal corrosion: chemical corrosion, electrochemical corrosion, and biological corrosion. Among them, "electrochemical corrosion" is the most common, that is, the oxidation reaction that is generally known, that is, the reaction of the metal itself with water and oxygen in the air, and finally the loss of electrons and the retention of oxides.

Why does metal lose electrons? It is because the "standard reduction potential difference" is lower than oxygen, so the electrons are taken away by the oxygen with high potential, resulting in structural damage and affecting the original characteristics. And this phenomenon of corrosion caused by the potential difference, we call it "potential corrosion"

Corrosion caused by two different metals

But what few people know is that when two different metals are put together, they actually accelerate corrosion. For example, if the window frame and the lock are made of different metals, the contact surface is easily corroded.

The reason why the dissimilar metal joint accelerates the corrosion is because different metals, such as iron, aluminum, steel, copper, etc., have different "potentials", just as the potential of iron is lower than oxygen, so it will cause rust. .

There is also a potential difference between the two metals, which will cause the metal with low potential to accelerate corrosion. On the contrary, the metal with high potential will be protected. For example, the standard reduction potential difference of copper is 0.34 volts, and the iron is - 0.44 volts. When connected, iron accelerates corrosion.

Although the problem of local corrosion does not cause a large loss of metal materials, it may cause sudden damage due to imperceptibility, and even unpredictable disasters. For example, if the pipeline is made of different metal materials, local perforation may occur. The situation that causes gas leakage and liquid outflow may cause fire or explosion.

Therefore, the problem of metal potential difference corrosion can not only look at the surface, but must establish the correct concept, and thoroughly prevent it. It must be isolated in places where there are joints of different metals, especially for hanging or fixing parts outside the building, otherwise it will be corroded. The resulting loss will not only be limited to materials and money, but will cause irreparable damage.


Ju Su Xin material co.,ltd can provide an effective solution for metal potential differential corrosion, efficient and qualified by government agencies.

Www.dwh.com.tw