Intergranular attack and intergranular stress corrosion cracking of Alloy 690 TT in high temperature lead‐containing caustic solution

Abstract

Immersion tests were carried out in high temperature lead‐containing caustic solution in a static autoclave. The results showed samples with three surface statuses of Alloy 690 TT suffered from intergranular attack (IGA) after immersion in 10% sodium hydroxide (wt%) with 10 g/L of litharge at 330 °C for different times. With the increasing immersion time, IGA became more severe. Wire cutting samples had the most serious IGA, ground samples followed and electro‐polished samples had the slightest IGA. IGA had developed into IGSCC only in wire cutting samples due to the existence of residual stress. All the specimens at different immersion time tests lost weight. To the same cold‐work samples, with the increasing immersion time, the weight loss increased. No IGA was found in 10% sodium hydroxide solution at 330 °C after 720 h immersion. When adding 100 ppm litharge into 10% sodium hydroxide solution, slight IGA was produced. IGA became more serious and the weight loss of the specimens with three surface statuses increased with the increase of lead concentration. As the results of 1% sodium hydroxide solution containing 10 g/L litharge and 4% sodium hydroxide solution containing 10 g/L litharge at 330 °C for 720 h immersion tests, only slight IGA occurred and the weight of samples with three surface statuses increased. The pH value played an important role in lead‐induced corrosion in caustic solution.

Corrosion of Alloy 690 in Simulated Steam Generator Crevices: Effect of Applied Potential, pH and Pb Addition

“…Redox potential, on the other hand, is strongly affected by e.g., copper content in the crevice solution. 7 There are many studies concerning PbSCC with Alloy 600, [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] and more recently Alloy 690, [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] whereas only a single study on stainless steel was found in the literature. 25 The inhibition of the dehydration process during passivation is proposed to be responsible for lead-induced passivity degradation, and it will result in the formation of anodic films containing more amorphous hydroxides and less crystalline (spinel) oxides.…”

Galvanic corrosion behavior of NiC filled conductive silicone rubber coupled to AZ31 magnesium alloys

“…Corrosion may occur when those equipments are used in high temperature [20][21], high humidity [22], and corrosive medium environment [23][24], which makes some component failure. There have been a lot of corrosion researches, such as stress corrosion [25][26][27], crevice corrosion [28], and galvanic corrosion, etc., on the metal materials specifically magnesium alloys. But the researches [29][30][31][32][33] of galvanic corrosion are focused mainly on the couple of Mg alloy and other metals.…”