IMPROVING THE CORROSION RESISTANCE OF PASSIVATING ALLOYS BY ALLOYING THE METAL SURFACE WITH PLATINUM GROUP METALS
Rubrics: 2. CHEMICAL TECHNOLOGY
Authors:
1.
Kazan National Research Technological University
2.
KNITU
3.
Kazan National Research Technological University
Kazan, Russian Federation
Kazan, Russian Federation
Type:
Article
Pages:
from 52
to 58
Status:
Published
Received:
07.08.2025
Accepted:
07.08.2025
Published:
07.08.2025
Language:
Russian
Keywords:
CHROMIUM-NICKEL STEEL, CHROMIUM COATING, TITANIUM ALLOY, SURFACE ALLOYING, SURFACE MODIFICATION, ELECTRODE POLARIZATION, PLATINUM GROUP METAL IONS
Abstract (English):
Based on a review of the literature, the protective effect of cathodic alloying with small amounts of electrochemically positive metals (Pd, Pt, Ru, Rh, etc.) has been demonstrated, which significantly increases the passivability and corrosion resistance of titanium, chromium, stainless steel, and a number of other alloys prone to passivation. Unlike bulk alloying, which increases the passivability of the alloy, i.e., slows down the kinetics of the anodic process and requires the introduction of a significant amount of alloying component, cathodic alloying, by reducing cathodic overvoltage and shifting the alloy potential towards positive values, can, under certain conditions, cause spontaneous passivation with insignificant additions of the cathodic component. As shown by research conducted in various countries, one way to increase the corrosion resistance of passivating alloys is to use effective cathodic additives to modify their surface. This review presents the current state of the art in the use of surface doping with noble metals to improve the passivability of various metals and alloys using a variety of methods, from electric spark surface treatment to electrodeposition. It is shown that local coatings of noble metals with a thickness of 10 nm already allow to increase the corrosion resistance of metals in aggressive environments (concentrated acids, chloride-containing solutions, etc.). It has been established that even partial destruction of the surface layer does not disturb the passive state of the metal. The main condition for a positive effect is the shift of the metal potential under these conditions to the region of stable passivity. The cathode current must exceed the limiting anode passivation current.
Based on a review of the literature, the protective effect of cathodic alloying with small amounts of electrochemically positive metals (Pd, Pt, Ru, Rh, etc.) has been demonstrated, which significantly increases the passivability and corrosion resistance of titanium, chromium, stainless steel, and a number of other alloys prone to passivation. Unlike bulk alloying, which increases the passivability of the alloy, i.e., slows down the kinetics of the anodic process and requires the introduction of a significant amount of alloying component, cathodic alloying, by reducing cathodic overvoltage and shifting the alloy potential towards positive values, can, under certain conditions, cause spontaneous passivation with insignificant additions of the cathodic component. As shown by research conducted in various countries, one way to increase the corrosion resistance of passivating alloys is to use effective cathodic additives to modify their surface. This review presents the current state of the art in the use of surface doping with noble metals to improve the passivability of various metals and alloys using a variety of methods, from electric spark surface treatment to electrodeposition. It is shown that local coatings of noble metals with a thickness of 10 nm already allow to increase the corrosion resistance of metals in aggressive environments (concentrated acids, chloride-containing solutions, etc.). It has been established that even partial destruction of the surface layer does not disturb the passive state of the metal. The main condition for a positive effect is the shift of the metal potential under these conditions to the region of stable passivity. The cathode current must exceed the limiting anode passivation current.
Keywords:
CHROMIUM-NICKEL STEEL, CHROMIUM COATING, TITANIUM ALLOY, SURFACE ALLOYING, SURFACE MODIFICATION, ELECTRODE POLARIZATION, PLATINUM GROUP METAL IONS
CHROMIUM-NICKEL STEEL, CHROMIUM COATING, TITANIUM ALLOY, SURFACE ALLOYING, SURFACE MODIFICATION, ELECTRODE POLARIZATION, PLATINUM GROUP METAL IONS
