Monitoring method for organic coating material carrier density

Abstract

The invention discloses a method for monitoring organic coating material carrier density. The invention includes the following steps: measure electrode base material is stainless steel stick which is sealed with epoxy resin, after the working surface is polished, cleaned and dried, the working surface is painted with organic coating material, the thickness of the painted film is controlled at 25 microns plus or minus 2 microns, and the working surface is constant temperature dried at 35 DEG C, then the membrane coated electrode is obtained; the membrane coated electrode is dipped in 5% sodium salt solution at room temperature, the saturated calomel is used as the assistant electrode, the platinum electrode is the reference electrode, the membrane coated electrode potential U and the capacitance Csc are measured; the relationship curve between the Csc-2 and U is drawn, and the Mott-Schottky relation schema is obtained; according to the Mott-Schottky relational expression, the Mott-Schottky relation schema is extrapolated to the crossing point of the potential axis, then the flat-band potential Ufb is obtained, at the same time the space charge density ND is calculated by slope, which is the carrier density.

Description

technical field [0001] The invention relates to a method for monitoring carrier density of an organic coating material. Background technique [0002] Organic coatings are widely used in metal facilities and devices to prevent corrosion and improve service life. Organic coatings are mainly composed of various resins, pigments, fillers, additives and dispersion media, which can play the role of anti-corrosion and decoration. With the increase of the life of the organic coating, due to the effects of ultraviolet rays, salt spray, pollutants and other factors, the physical and chemical properties of the coating itself will continue to deteriorate, aging and failure, and the anti-corrosion function of the metal substrate will continue to decline. Discoloration, chalking, cracking, blistering will occur, which in turn will cause the coating to peel off. The base structure will also corrode, and the most serious localized corrosion may even cause major failures or accidents. [...

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Problems solved by technology

[0004] Due to the lack of effective characterization means and experimental confirmation of the reaction mechanism of coating corrosion failure, it has not been understood until recent years. The reason is that the resistance of organic coatings is very high, and it is difficult to achieve non-destructive in-situ rapid measurement by general methods. , so the research on rapid, in-situ and non-destructive evaluation methods of coating properties has become a research hotspot in this field

At present, modern electrochemical research and evaluation methods of environmental failure of metal / organic coating systems at home and abroad include AC impedance technology, local AC impedance technology, scanning Kelvin probe technology, electrochemical noise technology, etc. These methods can be used from various To analyze the corrosion reaction at the coating / metal interface, but they all have a common weakness, that is, they cannot understand the cause of coating failure in essence

The organic coating has a good insulating effect, which reduces the electrochemical reaction between the metal body and the solution, and reduces the generation of corrosion products. However, when the organic coating fails due to electrolyte penetration, erosion, and doping, the internal coating The increase of carrier density, which in turn increases the formation of corrosion products, leading to the generation of small holes and cracks, and the coating eventually loses its protective effect.

As we all know, the main determinant of the performance of the insulating coating is its insulating performance, and the quality of the insulating performance has a great relationship with the carrier density in the coating. Therefore, the carrier density of the coating during the erosion process and its change with the erosion time should be used as an important indicator for evaluating and predicting the anti-corrosion performance of the coating.

However, none of the organic coating research methods used by the predecessors can evaluate the density behavior of carriers.

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