Metallic surface passivating film carrier density detection method

Abstract

The invention relate to a metallic surface passive film carrier density detection method, which comprises the following specific operational steps of taking a metal rod to be measured as a test electrode, dipping the test electrode in the electrolyte solution, taking a saturated calomel electrode as an auxiliary electrode, taking a platinum electrode as a reference electrode, and measuring the relation between the applied voltage U and the capacitance Csc of the metallic surface passive film electrode system; obtaining a Mott-Schottky graph of relation; then according to Mott-Schottky relation, extrapolating the Mott-Schottky graph of relation to the intersection point of electric potential shafts to work out a flat belt potential Ufb and simultaneously work out the metallic surface passive film carrier density according to a slope coefficient. The method which introduces the prior solid state physical band theory into the metallic anti-corrosion performance inspection and analysis field is capable of not only disclosing the cause for the reduction of anti-corrosion capability in the metallic surface passive film invalidation process substantially and microscopically-the increase of the carrier density, but also quantizing the metallic surface passive film anticorrosion performance through the simple mode of electrochemically measuring the carrier which is a physical quantity varying with the corrosion time and invalidation degree, thereby enabling the metallic anticorrosion performance and the passive film invalidation degree to be monitored in a better way and providing an effective method for metallic anticorrosion performance prediction.

Description

Technical field: [0001] The invention relates to a method for detecting the carrier density of a passivation film on a metal surface, which belongs to the field of metal anticorrosion performance detection. Background technique: [0002] Due to its excellent performance in many aspects such as strength, hardness, electrical conductivity, and thermal conductivity, metal materials have become an irreplaceable material in the social economy and people's lives. At the same time, as a strategic material, it plays a pivotal role in all aspects of society. . However, the chemical properties of most metal materials are relatively active, and they are easily transformed into corresponding oxides, hydrates, salts, etc. under the action of oxygen, water, and electrolyte solutions. This is what people often refer to as corrosion. Due to corrosion, the metal loses its due performance, which brings huge losses to the national economy and people's lives. According to relevant experts, on...

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Problems solved by technology

The passivation film cannot completely eliminate corrosion, because the passivation film will dissolve under certain conditions and lose its protective effect. Some metal passivation films have many defects. According to the point defect model (PDM), in the role of some ions The accumulation of carriers will occur in the barrier layer of the lower metal passivation film, and finally the barrier layer will collapse, thus losing its protection ability. Therefore, the barrier ability of the passivation film depends on the internal carrier density. Unfortunately, so far, no one has proposed to use the passivation film carrier density as an evaluation index of metal corrosion resistance.

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