The effect of the β phase (Al 12 Mg 17 ) on the corrosion resistance in a NaCl solution was investigated by electro chemical methods.Volume fraction of β phase in each specimen was controlled systematically by isothermal annealing at 473 K as 0%, 4%, 22% and 100 %, respectively. Although α phase shows lower corrosion current density than that of β phase, the α /β mixed phase specimen showed higher corrosion current density than that of α phase.It strongly suggests that β phase act as cathodic electrode in the alloys.

Fe-Cu-C sintered steels are widely used as powder materials, because of its small volumetric shrinkage. However, Cu, which acts as cathode enhance formation of rust (Fe 2 O 3 ·xH 2 O) during fabrication. To prevent formation of Fe 2 O 3 ·xH 2 O rust preventive oils are genially used. Therefore, it is necessary to develop new rust preventive oils with contradictory properties of low viscosity and superior rust prevention. In this study, we developed technique to quantitatively evaluate rust prevention ability by measuring polarization curve through thin corrosive solution on Fe-Cu-C sintered steels coated with rust preventive oils. Polarization curves were registered after 30 min of exposure to test solution in order to allow corrosion potential (E corr ) stabilization. From the experimental, it is possible to evaluate the corrosion rate quantitatively in the surface of specimen, which was coated with rust preventive oil through thin corrosive solution. The measurement results suggest the anodic reaction is decreased with oils.

Fe-Cu-C sintered steels are widely used as powder materials, because of its small volumetric shrinkage. However, Cu, which acts as cathode enhance formation of rust Fe 2 O 3 ·xH 2 O during fabrication. To prevent formation of Fe 2 O 3 ·xH 2 O rust preventive oils are widely used. High viscosity of those rust preventive oils decrease workability. While, low viscosity degrade rust preventive performance. Therefore, it is necessary to develop new rust preventive oils with contradictory properties of low viscosity and superior rust prevention. In this study, we developed technique to quantitatively evaluate rust prevention ability by measuring polarization curve through thin corrosive solution on Fe-Cu-C sintered steels coated with rust preventive oils. The electrochemical measurements were carried out in corrosive solution of 0.35 mass % NaCl. Using a double capillary was added dropwise to the specimen. From the experimental, it is possible to evaluate the corrosion rate quantitatively in the surface of specimen, which was coated with rust preventive oil through thin corrosive solution. From the measurement results, Corrosion rate is reduced by coating the rust preventive oil. Especially, corrosion rate of the specimen coated with oil that showed best performance indicated 10000 times better than that of without oil ones. Zn addition negative correlation between corrosion rate and period of potential oscillation.Keywords: sintered steel, polarization curve, rust preventive oil Spiekane stale Fe-Cu-C są szeroko stosowane jako materiały proszkowe, ze względu na mały skurcz objętościowy. Jednak miedź, która zachowuje się jak katoda, wpływa na zwiększone powstawanie rdzy Fe 2 O 3 ·xH 2 O w procesie wytwarzania stali. Aby zapobiec tworzeniu się Fe 2 O 3 ·xH 2 O stosuje się oleje ochronne. Jednak wysoka lepkość olejów zmniejsza ich urabialność, natomiast niska lepkość zmniejsza ich właściwości ochronne. Z tych względów konieczne jest opracowanie nowego typu olejów przeciwrdzewnych charakteryzujących się zarówno niską lepkością jak i dobrymi właściwościami ochronnymi. W niniejszej pracy opracowano metodę ilościowej oceny właściwości ochronnych olejów za pomocą pomiaru krzywej polaryzacji poprzez cienką warstwę roztworu korozyjnego na spiekanych stalach Fe-Cu-C pokrytych olejami ochronnymi. Pomiary elektrochemiczne zostały przeprowadzone w roztworze korozyjnym NaCl (0,35 %wag.). Roztwór został naniesiony na próbkę za pomocą kapilary. Na podstawie wyników eksperymentalnych można ilościowo oszacować szybkość korozji zachodzącej na powierzchni próbki. Badania wykazały, że olej ochronny zmniejsza szybkość korozji. Olej dla którego otrzymano najlepsze wyniki wykazał poprawę właściwości ochronnych 10000 krotnie w porównaniu z próbkami bez oleju. Dodatkowo stwierdzono korelację pomiędzy szybkością korozji a okresem oscylacji potencjału.

FeCuC sintered steel is prone to rust, therefore rust preventive oil is used for storage. These rust preventive oils generally have a problem of reduced workability due to stickiness caused by high viscosity. However, few electrochemical studies have been conducted on the correlation between viscosity and corrosion resistance. Therefore, in this study, we investigated the effect of the base oil viscosity on the corrosion resistance of rust preventive oil by changing the base oil viscosity.As an experimental method, electrochemical measurements were carried out using the water screen test established in our laboratory, which can quantitatively evaluate the rust preventing ability. According to the polarization curves measurements, corrosion current density I corr is reduced by coating the rust preventive oil. It showed about 100,000 times better corrosion resistance with and without rust preventive oil. While, almost no difference in rust preventive ability was confirmed due to the difference in base oil viscosity. According to the results of the open circuit potential, the time required for the potential of FeCuC sintered steel to saturate was 505 ks for low viscosity, 651 ks for medium viscosity, and 340 ks for high viscosity. Therefore, it was found that there is no correlation between the time until rust occurs and the viscosity of the oil film. It was also found that the effects of the additives were fully exerted even if the oil viscosities were different. Therefore, the problem of reduced workability due to stickiness can be solved by using low viscosity base oil.