国产精品久久久久久久久,四季AV一区二区夜夜嗨,日韩精品无码中文字幕电影,www.五月婷婷.com

埋地管線防腐陽極供應(yīng)商-鎂合金犧牲陽極權(quán)威廠家

 

根據(jù)鋁和鋅的含量不同，性能不同，其中性能較好和獲得廣泛應(yīng)用的主要是Mg-6Al-3Zn-Mn合金，其表面溶解均勻，電流效率大于50%.鋁是陽極中的主要合金元素，可與鎂形成Mg17 A112強(qiáng)化相，提高合金的強(qiáng)度。但向工業(yè)鎂中單獨(dú)添加鋁時(shí)，可形成大量的Mg Al, Mg2A13, Mg4 A13等金屬間化合物，這些金屬間化合物的存在，都會(huì)增大鎂的自腐蝕速度、加速固溶體的破壞。鋅可降低鎂的腐蝕率，減小鎂的負(fù)差異效應(yīng)，提高陽極電流效率。微量的錳可抵消雜質(zhì)鐵、鎳的不良影響。當(dāng)錳的添加量為0.3%時(shí)，可使鐵的允許含量達(dá)到0.02%，但同時(shí)也會(huì)降低電流效率。因此，雜質(zhì)鐵的含量以及相應(yīng)的錳含量應(yīng)盡可能低。鋁、鋅、錳的同時(shí)存在可進(jìn)一步降低對(duì)工業(yè)鎂中的雜質(zhì)元素含量的要求。為了獲得良好的電化學(xué)性能，Mg-AI-Zn-Mn系合金的雜質(zhì)含量應(yīng)嚴(yán)格控制。在相近的合金成分條件下，雜質(zhì)少的合金的電流效率明顯高于含雜質(zhì)多的合金。

  陰極保護(hù)是基于電化學(xué)腐蝕原理的一種防腐蝕手段。美國腐蝕工程師協(xié)會(huì)對(duì)陰極保護(hù)的定義是：通過施加外加的電動(dòng)勢把電極的腐蝕電位移向氧化性較低的電位而使腐蝕速率降低。犧牲陽極陰極保護(hù)就是在金屬構(gòu)筑物上連接或焊接電位較負(fù)的金屬,如鋁、鋅或鎂。陽極材料不斷消耗,釋放出的電流供給被保護(hù)金屬構(gòu)筑物而陰極極化，從而實(shí)現(xiàn)保護(hù)。外加電流陰極保護(hù)是通過外加直流電源向被保護(hù)金屬通以陰極電流，使之陰極極化。該方式主要用于保護(hù)大型或處于高土壤電阻率土壤中的金屬結(jié)構(gòu)。 [1]

  保護(hù)電位是指陰極保護(hù)時(shí)使金屬腐蝕停止（或可忽略）時(shí)所需的電位。實(shí)踐中，鋼鐵的保護(hù)電位常取-0.85V（CSE），也就是說，當(dāng)金屬處于比-0.85V（CSE）更負(fù)的電位時(shí)，該金屬就受到了保護(hù)，腐蝕可以忽略。

 

According to the different contents of aluminum and zinc, the properties are different. among them, mg - 6al - 3zn - Mn alloy, which has better properties and is widely used, has a unib surface dissolution and a current efficiency of more than 50 %. aluminum is the main alloy element in the anode and can b a mg17a112 strengthening phase with magnesium to improve the strength of the alloy.  However, when aluminum is added to industrial magnesium alone, a large amount of interbllic compounds such as mg al, mg2a13, mg4a13 can be bed. the existence of these interbllic compounds will increase the self-corrosion rate of magnesium and accelerate the destruction of solid solution.  Zinc can reduce the corrosion rate of magnesium, reduce the negative differential effect of magnesium, and improve the efficiency of anode current.  Trace amount of manganese can offset the adverse effects of impurities such as iron and nickel.  When the amount of manganese added is 0.3 %, the allowable content of iron can reach 0.02 %, but at the same time the current efficiency can also be reduced.  Therefore, the content of impurity iron and corresponding manganese should be as low as possible.  The simultaneous presence of aluminum, zinc and manganese can further reduce the requirements for impurity elements in industrial magnesium.  In order to obtain good electrochemical perbance, the impurity content of mg - ai - Zn - Mn alloy should be strictly controlled.  Under similar alloy comb conditions, the current efficiency of alloys with less impurities is obviously higher than that of alloys with more impurities.
 Cathodic protection is an anti-corrosion b based on electrochemical corrosion principle.  The American society of corrosion engineers defines cathodic protection as the reduction of corrosion rate by applying an applied electromotive force to shift the corrosion electricity of the electrode to a potential with lower oxidation.  Sacrificial anode cathodic protection is to connect or weld bls with negative potential on bl structures, such as aluminum, zinc or magnesium.  The anode material is continuously consumed, and the released current is supplied to the protected bl structure while the cathode is polarized, thus realizing protection.  Impressed current cathodic protection is to apply cathodic current to the protected bl through an impressed DC power supply to polarize it.  This b is mainly used to protect bl structures in large or high soil resistivity soils.  [1]
 The protection potential refers to the potential required to stop ( or ignore ) bl corrosion during cathodic protection.  In practice, the protective potential of steel is usually - 0.85 v ( CSE ), that is, when the bl is at a more negative potential than - 0.85 v ( CSE ), the bl is protected and corrosion can be neglected.

1193178453