Q&A on Financial Prospects II: The Passivation Phenomenon of Metals

Answer: The passivation of metals can be divided into chemical passivation and electrochemical passivation. For example, iron dissolves quickly in dilute nitric acid, but the dissolution process almost completely stops in concentrated nitric acid ； Aluminum is very unstable in dilute nitric acid, but aluminum containers can be used to store concentrated nitric acid ； Carbon steel rusts easily in normal atmospheric conditions, but when an appropriate amount of chromium-nickel alloying elements is added to it, it becomes \"stainless steel\". These passivation phenomena are called chemical passivation. Another type of passivation phenomenon is caused by anodic polarization and is called electrochemical passivation. In fact, most cases of chemical passivation also proceed according to electrochemical mechanisms, as significant changes in electrode potential can be observed during chemical passivation as well. The potential of iron in the activated state is approximately -0.5 to -0.2 volts, while in the passivated state it is +0.5 to +1 volt. The potential of chromium in the activated state is -0.6 to -0.4 volts, while in the passivated state it is +0.8 to +1 volt. Therefore, passivation can cause the electrode potential to shift sharply in the positive direction, bringing the potential of the passivated metal to be approximately equal to that of precious metals such as gold and platinum. Although the occurrence of the blunt effect is relatively frequent and quite noticeable, there is still no unified and definitive explanation for it to date. According to the theory of electrochemical corrosion, passivity is a highly corrosion-resistant state of metals or alloys resulting from a hindrance in the cathodic process (although, from a thermodynamic perspective, these metals and alloys are fully capable of undergoing reactions). In other words, passivity is a corrosion-resistant state resulting from increased control of the anodic process.

This post was last edited by jaho on 2009-11-2 at 16:01. The passivation of metals can be divided into two categories: chemical passivation and electrochemical passivation. For example, iron dissolves quickly in dilute nitric acid, but the dissolution process almost completely stops in concentrated nitric acid ； Aluminum is very unstable in dilute nitric acid, but aluminum containers can be used to store concentrated nitric acid ； Carbon steel rusts easily in normal atmospheric conditions, but when an appropriate amount of chromium-nickel alloying elements is added to it, it becomes \"stainless steel\". These passivation phenomena are called chemical passivation. Another type of passivation phenomenon is caused by anodic polarization and is called electrochemical passivation. In fact, most cases of chemical passivation also proceed according to electrochemical mechanisms, as significant changes in electrode potential can be observed during chemical passivation as well. The potential of iron in the activated state is approximately -0.5 to -0.2 volts, while in the passivated state it is +0.5 to +1 volt. The potential of chromium in the activated state is -0.6 to -0.4 volts, while in the passivated state it is +0.8 to +1 volt. Therefore, passivation can cause the electrode potential to shift sharply in the positive direction, bringing the potential of the passivated metal to be approximately equal to that of precious metals such as gold and platinum. Although the occurrence of the blunt effect is relatively frequent and quite noticeable, there is still no unified and definitive explanation for it to date. According to the theory of electrochemical corrosion, passivity is a highly corrosion-resistant state of metals or alloys resulting from a hindrance in the cathodic process (although, from a thermodynamic perspective, these metals and alloys are fully capable of undergoing reactions). In other words, passivity is a corrosion-resistant state resulting from increased control of the anodic process.

The passivation of metals can be divided into chemical passivation and electrochemical passivation. For example, iron dissolves quickly in dilute nitric acid, but the dissolution process almost completely stops in concentrated nitric acid ； Aluminum is very unstable in dilute nitric acid, but aluminum containers can be used to store concentrated nitric acid ； Carbon steel rusts easily in normal atmospheric conditions, but when an appropriate amount of chromium-nickel alloying elements is added to it, it becomes \"stainless steel\". These passivation phenomena are called chemical passivation. Another type of passivation phenomenon is caused by anodic polarization and is called electrochemical passivation. In fact, most cases of chemical passivation also proceed according to electrochemical mechanisms, as significant changes in electrode potential can be observed during chemical passivation as well. The potential of iron in the activated state is approximately -0.5 to -0.2 volts, while in the passivated state it is +0.5 to +1 volt. The potential of chromium in the activated state is -0.6 to -0.4 volts, while in the passivated state it is +0.8 to +1 volt. Therefore, passivation can cause the electrode potential to shift sharply in the positive direction, bringing the potential of the passivated metal to be approximately equal to that of precious metals such as gold and platinum. Although the occurrence of the blunt effect is relatively frequent and quite noticeable, there is still no unified and definitive explanation for it to date. According to the theory of electrochemical corrosion, passivity is a highly corrosion-resistant state of metals or alloys resulting from a hindrance in the cathodic process (although, from a thermodynamic perspective, these metals and alloys are fully capable of undergoing reactions). In other words, passivity is a corrosion-resistant state resulting from increased control of the anodic process.

Metal passivation involves forming a passivation layer on the metal surface, which prevents the oxides from further oxidizing the inner parts of the metal; this layer acts as a protective barrier for the internal metal.

Metal passivation involves forming a passivation layer on the metal surface, which prevents the oxides from further oxidizing the inner parts of the metal; this layer acts as a protective barrier for the internal metal. 1# A promising financial future

The phenomenon in which the corrosion resistance of a metal or alloy increases due to a blockage of the anodic reaction is called passivation. The formation of passivation occurs through the following two pathways. 1 Chemical passivation: Passivation is achieved through the natural reaction of an oxidizing agent (passivator) with the metal. 2 Electrochemical passivation (anodic passivation) involves passivation by anodizing using an external current. Passivation can cause the electrode potential to shift sharply in the positive direction, bringing the potential of the passivated metal to be approximately equal to that of precious metals such as gold and platinum.

The passivation of metals can be divided into chemical passivation and electrochemical passivation. For example, iron dissolves quickly in dilute nitric acid, but the dissolution process almost completely stops in concentrated nitric acid ； Aluminum is very unstable in dilute nitric acid, but aluminum containers can be used to store concentrated nitric acid ； Carbon steel rusts easily in normal atmospheric conditions, but when an appropriate amount of chromium-nickel alloying elements is added to it, it becomes \"stainless steel\". These passivation phenomena are called chemical passivation. Another type of passivation phenomenon is caused by anodic polarization and is called electrochemical passivation. In fact, most cases of chemical passivation also proceed according to electrochemical mechanisms, as significant changes in electrode potential can be observed during chemical passivation as well. The potential of iron in the activated state is approximately -0.5 to -0.2 volts, while in the passivated state it is +0.5 to +1 volt. The potential of chromium in the activated state is -0.6 to -0.4 volts, while in the passivated state it is +0.8 to +1 volt. Therefore, passivation can cause the electrode potential to shift sharply in the positive direction, bringing the potential of the passivated metal to be approximately equal to that of precious metals such as gold and platinum. Although the occurrence of the blunt effect is relatively frequent and quite noticeable, there is still no unified and definitive explanation for it to date. According to the theory of electrochemical corrosion, passivity is a highly corrosion-resistant state of metals or alloys resulting from a hindrance in the cathodic process (although, from a thermodynamic perspective, these metals and alloys are fully capable of undergoing reactions). In other words, passivity is a corrosion-resistant state resulting from increased control of the anodic process.

The passivation of metals can be divided into chemical passivation and electrochemical passivation. For example, iron dissolves quickly in dilute nitric acid, but the dissolution process almost completely stops in concentrated nitric acid ； Aluminum is very unstable in dilute nitric acid, but aluminum containers can be used to store concentrated nitric acid ； Carbon steel rusts easily in normal atmospheric conditions, but when an appropriate amount of chromium-nickel alloying elements is added to it, it becomes \"stainless steel\". These passivation phenomena are called chemical passivation. Another type of passivation phenomenon is caused by anodic polarization and is called electrochemical passivation. In fact, most cases of chemical passivation also proceed according to electrochemical mechanisms, as significant changes in electrode potential can be observed during chemical passivation as well. The potential of iron in the activated state is approximately -0.5 to -0.2 volts, while in the passivated state it is +0.5 to +1 volt. The potential of chromium in the activated state is -0.6 to -0.4 volts, while in the passivated state it is +0.8 to +1 volt. Therefore, passivation can cause the electrode potential to shift sharply in the positive direction, bringing the potential of the passivated metal to be approximately equal to that of precious metals such as gold and platinum. Although the occurrence of the blunt effect is relatively frequent and quite noticeable, there is still no unified and definitive explanation for it to date. According to the theory of electrochemical corrosion, passivity is a highly corrosion-resistant state of metals or alloys resulting from a hindrance in the cathodic process (although, from a thermodynamic perspective, these metals and alloys are fully capable of undergoing reactions). In other words, passivity is a corrosion-resistant state resulting from increased control of the anodic process.

The process in which changes in the surface condition of a metal lead to changes in its electrochemical behavior, endowing it with certain characteristics of precious metals (low corrosion rate, positive electrode potential).

We know that iron and aluminum dissolve rapidly in dilute HNO3 or dilute H2SO4, but the dissolution process almost comes to a halt in concentrated HNO3 or concentrated H2SO4. Carbon steel tends to rust easily; however, by adding an appropriate amount of Ni and Cr to the steel, stainless steel is obtained. The phenomenon in which the chemical stability of a metal or alloy increases significantly as a result of certain factors is known as passivation.