Modification of magnetic coatings formed on steel in nitrate solutions

To improve the protective and technological properties of magnetite coatings (MC) formed on mild steel in solutions of ammonium nitrate, they were modified with a nitrogen-containing additive MD-3. The influence of the concentration of reagents and the temperature of the process on the thickness and stability of the magnetic field is analyzed. It is shown that both at high (100 ° C) and low (≤ 70 ° C) temperatures, the MC is loose. In the presence of the MD-3 additive, the optimal values of the concentration of ammonium nitrate and the temperature range are determined, which makes it possible to obtain the most stable MC. The analysis of the main lines of magnetite, obtained by the method of X-ray diffraction on steel with a conventional or modified MC, is carried out. It is shown that in the presence of MD-3 in the solution, in addition to the formation of magnetite, the formation of an amorphous phase of iron hydroxide occurs, and the size of magnetite crystallites decreases by a factor of 1.5 - 2.0 compared to the unmodified coating. It is shown that in presence of MD-3 the MC becomes more homogeneous and thinner than that formed in a pure solution. Various corrosion tests showed a linear increase of the protective properties of modified MCs with respect to the time of oxidizing.