Inhibitor Protection of Raw-Water Heaters against Corrosion and Scaling

We propose a new technological procedure aimed at the protection of pipes of raw-water heaters made of 20 steel against corrosion and scaling by using the KORSOL-1M inhibitor (based on phosphates). For the optimal concentration of the inhibitor C _inh = 200 mg/liter, the time of continuous operation of heat-exchange pipes of raw-water heaters increases up to 5–6 months. During the downtime, it is reasonable to apply soft chemical cleaning because the layer of scale on the steel surface become amorphous and thin ( 1 mm) and can easily be removed from the surface. The time of chemical cleaning is halved. In raw water, the KORSOL-1M inhibitor does not impair the operation of the subsequent chain of mechanical and ion-exchange filters.     

Effect of the range of particle sizes on the heat resistance of chrome-nickel alloys

We study the effect of the range of particle sizes in KhN45Yu alloy and 12Kh18N10T and 15Kh25T steels on their heat resistance at temperatures of 800, 1000, and 1200°C in air on a base of up to 1000 h. It is shown that materials with a coarse-grained structure exhibit a much higher oxidation susceptibility than those with a fine-grained structure. For the materials under investigation, the oxidation rates are greater in the stressed state and increase as a result of thermal cycling.Translated from Fiziko-Khimicheskaya Mekhanika Materialov, Vol. 30, No. 5, pp. 45–49, September–October, 1994.     

Corrosion Behavior of α-Fe and 20kh13 Steel in Contact with Oxygen-Containing Lead Melts

We study the structure and chemical composition of the reaction products formed in the process of contact of -Fe and 20Kh13 steel with oxygen-containing stagnant lead melts (600–700°C, 3000 h, C _O[Pb] (1–4) · 10^–5 wt.%). It is shown that a heterogeneous structure is formed in the interaction zone. This structure consists of an external intermediate layer (with low hardness, the same composition as the matrix, and lead accumulated on the grain boundaries) and a thin oxide film (Fe₃O₄ for -Fe and FeCr₂O₄ and Cr₂O₃ for 20Kh13 steel), which separates the intermediate layer from the internal porous suboxide layer of the matrix and blocks the process of penetration of lead into the matrix.     

Corrosion of armco iron and model Fe−Cr-Al alloys in oxygen-containing lead melts

We studied the influence of oxygen-containing (6·10⁻³ wt.% O) lead on the corrosion of Armco iron and Fe−16Cr, Fe−16Cr−1Al alloys at a temperature of 650°C under stationary conditions. The front of corrosion propagates according to a linear law and this process is periodically repeated. In each period, an oxide film based on Fe₃O₄ magnetite is formed on the surface of the metal and lead penetrates into the suboxide zone. This leads to the exfoliation the external oxide film and then the process is repeated. Under the indicated testing conditions, alloying with chromium and aluminum intensifies the process of corrosion in iron. Karpenko Physicomechanical Institute, Ukrainian Academy of Sciences, L'viv. Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 33, No. 2, pp. 84–88, March–April, 1997.     

Effect of admixtures of oxygen on the oxidation of iron and Fe−Cr alloys in lead melts

We study the process of oxidation of Armco iron and Fe−16Cr and Fe−16Cr−1Al model alloys held in lead melts with different concentrations of oxygen for 1000 h at 650°C. It was discovered that the intensity of oxidation, the structure, and phase composition of oxide layers are determined by the activity of oxygen in the liquid metal. By the methods of layer-by-layer X-ray diffraction analysis and microscopic X-ray diffraction analysis, it was shown that, for low concentrations of oxygen in lead (C ₀≤10⁻⁶ wt.%), a thin (1–5μm) oxide [magnetite (Fe₃O₄] film is formed on the surface of iron. If alloys are held under the same conditions, then we also observe an increase in the concentration of chromium in the subsurface layers. For higher concentrations of oxygen (up to 10⁻⁵ wt.%), a film of magnetite (with inclusions of pure lead) is formed on the surface of unalloyed iron. In alloys, under the layer of magnetite, we detect the formation of oxide layers with the same composition as a solid solution of Fe₃O₄ and FeCr₂O₄ and the structure of spinel. These layers efficiently suppress the process of penetration of lead but do not completely terminate the process of diffusion of oxygen into the bulk of the material, which eventually leads to the internal oxidation of alloy. Karpenko Physicomechanical Institute, Ukrainian Academy of Sciences, L'viv. Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 33, No. 3, pp. 97–101, May–June, 1997.