апрель 2019

Potential dinamic study of basis of the austinite steel AISI 316 pitting resistance on ultrasonic vibration

N. S. Berehova , D. V. Maltseva , H. S.Vasyliev
Химия и современные технологии
Abstract / Full Text

In the heat points of modern apartment buildings, effective and small-sized lamellar heat exchangers are installed. However, when heating natural waters without preliminary preparation, there is a problem of pitting corrosion of heat exchange plates and formation of scale on the surface of heat exchange. The result of pitting corrosion is the through perforation of the plates, caused by the water from the water supply system, which enters the heat network and causes damage to the pipelines and the formation of sediments in boilers.

According to modern data, the promising method of reducing the rate of pitting corrosion is the use of ultrasonic cavitation. However, due to the small radius of propagation of the cavitation field in the liquid, it is more appropriate to use ultrasonic vibration to control the pitting corrosion of austenitic steels.

The study of the influence of ultrasonic vibration on pitting corrosion was carried out in accordance with GOST 9.912-89 and consisted in determining the basis of the resistance of the steel with vibration and without vibration. The sample of AISI 316 steel with a working surface of 4 cm2 was pressed to the end of an ultrasonic emitter operating at a frequency of 27 kHz with a power consumption of 10 W. The steel was polarized to the anode side in a solution of 3.5% NaCl at a velocity of 2·10–4 V/s until the anode current appeared with the density of 15 μA / cm2. After activation, the polarization was changed to a cathode one.

Figure 1 – Potetidynamic curves of AISI 316 steel in 3.5% NaCl: 1 − without ultrasound; 2 − with ultrasonic vibra-tion.

According to the data obtained, under the action of ultrasonic vibration, the steel activation potential has shifted at 50 mV to the anode side, while the rehabilitation potential has also shifted to almost 100 mV to the anode side. Thus, the imposition of ultrasonic vibration can increase the resistance of AІSI 316 steel to pitting corrosion.