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hydrogen embrittlement caused by evolution of hydrogen due to the reduction
reaction of bicarbonate ions.
The influence of long-term operation of the welded joint of the 17Г1С
pipeline steel on the characteristics of corrosion resistance, resistance to stress
corrosion cracking and corrosion fatigue has been analysed. It has been found that
long-term operation of the butt weld of the 17Г1С pipeline steel reduces resistance
of the metal of different zones to hydrogen cracking in NS4, which simulates the
soil environment solution, by 2.3-13 times. The threshold stress intensity factor for
corrosion fatigue crack growth in the welded joint of this steel in NS4 solution is
most intensively reduced by a combination of a number of factors: long-term
operation, high loading-cycle asymmetry R = 0.9 and cathodic protection potential
E cp (-0.98 V). Under such conditions, values of corrosion fatigue crack growth rate
in the plateau area for the operated base metal and weld metal are 1.5 and 2.6 times
higher, respectively, compared to the as-received condition.
Scientific novelty of the obtained results.
It was established that cavitation under combined action with cyclic loading
significantly reduces the characteristics of corrosion fatigue durability of the 35
steel in tap water: the corrosion fatigue limit is reduced by 2.4 times, and limited
durability for loads close to the fatigue limit – by an order of magnitude.
For the first time, the effectiveness of inhibitor protection of the 30ХГСНА
steel against corrosion cavitation damage in tap water with triethylammonium
iodide, which provides a degree of protection of 90-97% depending on the
intensity of cavitation loading, was revealed.
It was established that the resistance of the 17Г1С steel to fracture at a constant
deformation rate of 10 s in 0.01 N aqueous solution of NaHCO 3 with the addition
-7 -1
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3-
2-
of anions (0.005 N) Сl , NO 3 , CO 3 і PO 4 decreases with increasing cathodic
polarization, does not depend on intensity of local corrosion and increases with
improvement of barrier properties of the corrosion products inhibiting hydrogenation
of the metal. In deaerated aqueous bicarbonate solution, the main mechanism of
corrosion-mechanical fracture of the steel is hydrogen embrittlement caused by