Use of Hydrazine for Pitting Corrosion Inhibition of Copper Sprinkler Tubes: Reaction of Hydrazine with Corrosion By-Products

( Sang Hee Suh ),( Sohee Kim ),( Youngjoon Suh ) 한국부식방식학회(구 한국부식학회) 2017 Corrosion Science and Technology Vol.16 No.5

The feasibility of using hydrazine for inhibiting pitting corrosion in copper sprinkler tubes was investigated by examining microscopical and structural evolution of corrosion by-products with SEM, EDS, and XRD. Hydrazine removed dissolved oxygen and reduced CuO and Cu₂O as well. The stable phase was changed from CuO to Cu₂O or Cu depending on hydrazine concentration. Hydrazine concentration of 500 ppm could convert all CuO corrosion by-products to Cu₂O. In a tightly sealed acryl tube filled with aqueous solution of 500 ppm hydrazine, octahedral Cu₂O particles were formed while plate-like structures with high concentration of Cu, O, N and C were formed near a corrosion pit. The inside structure of a corrosion pit was not altered by hydrazine aqueous solution. Uniform corrosion of copper was almost completely stopped in aqueous solution of 500 ppm hydrazine. Corrosion potential of a copper plate was linearly dependent on log (hydrazine concentration). The concept of stopping pitting corrosion reaction by suppressing oxygen reduction reaction could be verified by applying this method to a reasonable number of real sprinkler systems before full-scale application.

Comparative Study on Pitting Corrosion of Copper Tubes in Pitting and Fitting-Free Area

Sakai, Masahiro,Seri, Osami 한국부식방식학회 2002 Corrosion Science and Technology Vol.31 No.3

Field tests for the copper tube in the area where pitting corrosion has often occurred were carried out in order to investigate the initiation and the propagation of pits. For a comparative study, we installed the same field equipment in two areas (pitting and pitting-free areas) to measure the corrosion potential of copper tubes and the electric conductivity of tap water. The electric conductivity in the pitting area was higher than that in the pitting-free area during the whole period of examination. It was found that the pitting corrosion has occurred in both pitting and pitting-& areas, but the maximum pit in the pitting area after 12 months was about three times deeper than that in the pitting-free area after 12 months.

Effects of Sigma (σ) Phase on the Pitting Corrosion of 25% Cr Duplex Stainless Steel : Investigations by means of Electrochemical Noise Measurement

Park, Chan-Jin,Kwon, Hyuk-Sang,Kim, Hee-San 한국부식방식학회 2003 Corrosion Science and Technology Vol.2 No.1

Effects of the precipitation of a phase on the metastable pitting as a precursor of stable pitting corrosion and also on the progress of stale pitting of the 25Cr-7Ni-3Mo-0.25N duplex stainless steel were investigated in chloride solution. Electrochemical potential and current noises of the alloy were measured in 10 % ferric chloride solution (FeCl₃) with zero resistance ammeter (ZRA), and then analyzed by power spectral density (PSD) and by corrosion admittance (A_c) spectrum. With aging at 850℃, the passive film of the alloy was found to get significantly unstable as represented by power spectral density (PSD) and a transition from metastable pitting state to stable one was observed. In the corrosion admittance spectrum, the number of negative A_c. corresponding to the state of localized corrosion increased with aging, suggesting that the precipitation of a phase considerably degraded the passive film by depleting Cr and Mo around it at α/σ or γ/σ phase boundaries, thereby leading to the initiation of the pitting corrosion. However, the Cr and Mo at α/σ or γ/σ phase boundaries which were once depleted due to the precipitation of the σ phase were partly replenished by the difhsion of Cr and Mo from the surrounding matrix with aging time longer. The initiation of pitting seems to be associated with the precipitation density of the σ phase with an effective size needed to induce the sufficient depletion of Cr and Mo around it.

스프링클러 구리배관의 공식 파손 억제

서상희 ( Sang Hee Suh ),서영준 ( Youngjoon Suh ),이종혁 ( Jonghyuk Lee ),권혁상 ( Hyuksang Kwon ) 한국부식방식학회(구 한국부식학회) 2020 Corrosion Science and Technology Vol.19 No.2

The inhibition of pitting corrosion failure of copper sprinkler tubes in wet sprinkler systems was studied. First, an apparatus and technology for removing air in the sprinkler tubes by vacuum pumping and then filling the tubes with water were developed. Using this apparatus and technology, three methods for inhibiting the pitting corrosion of the copper sprinkler tubes installed in several apartment complexes were tested. The first one was filling the sprinkler tubes with water bubbled by high-pressure nitrogen gas to reduce the dissolved oxygen concentration to lower than 2 ppm. In the second method, the dissolved oxygen concentration of water was further reduced to lower than 0.01 ppm by sodium sulfite. In the third method, the sprinkler tubes were filled with benzotriazole (BTAH) dissolved in water. The third method was the most effective, reducing the failure frequency of the sprinkler tubes due to pitting corrosion by more than 80%. X-ray photoelectron spectroscopy analyses confirmed that a Cu-BTA layer was well coated on the inside surface of the corrosion pit, protecting it from corrosion. A potentiodynamic polarization test showed that BTAH should be very effective in reducing the corrosion rate of copper in the acidic environment of the corrosion pit.

Pitting Corrosion Inhibition of Sprinkler Copper Tubes via Forming of Cu-BTA Film on the Inner Surface of Corrosion pits

( Sang Hee Suh ),( Youngjoon Suh ),( Sohee Kim ),( Jun-mo Yang ),( Gyungtae Kim ) 한국부식방식학회(구 한국부식학회) 2019 Corrosion Science and Technology Vol.18 No.2

The feasibility of using benzotriazole (BTAH) to inhibit pitting corrosion in the sprinkler copper tubes was investigated by filling the tubes with BTAH-water solution in 829 households at an eight-year-old apartment complex. The water leakage rate was reduced by approximately 90% following BTAH treatment during 161 days from the previous year. The leakage of one of the two sprinkler copper tubes was investigated with optical microscopy, scanning electron microscopy, energy dispersive spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction analysis to determine the formation of Cu-BTA film inside the corrosion pits. All the inner components of the corrosion pits were coated with Cu-BTA films suggesting that BTAH molecules penetrated the corrosion products. The Cu-BTA film was about 2 nm in thickness at the bottom of a corrosion pit. A layer of CuCl and Cu₂O phases lies under the Cu-BTA film. This complex structure effectively prevented the propagation of corrosion pits in the sprinkler copper tubes and reduced the water leakage.

Lateral impact behaviour of concrete-filled steel tubes with localised pitting corrosion

Gen Li,Chao Hou,Luming Shen,Chuan-Chuan Hou 국제구조공학회 2023 Steel and Composite Structures, An International J Vol.47 No.5

Steel corrosion induces structural deterioration of concrete-filled steel tubes (CFSTs), and any potential extreme action on a corroded CFST would pose a severe threat. This paper presents a comprehensive investigation on the lateral impact behaviour of CFSTs suffering from localised pitting corrosion damage. A refined finite element analysis model is developed for the simulation of locally corroded CFSTs subjected to lateral impact loads, which takes into account the strain rate effects on concrete and steel materials as well as the random nature of corrosion pits, i.e., the distribution patterns and the geometric characteristics. Full-range nonlinear analysis on the lateral impact behaviour in terms of loading and deforming time-history relations, nonlinear material stresses, composite actions, and energy dissipations are presented for CFSTs with no corrosion, uniform corrosion and pitting corrosion, respectively. Localised pitting corrosion is found to pose a more severe deterioration on the lateral impact behaviour of CFSTs due to the plastic deformation concentration, the weakened confinement and the reduction in energy absorption capacity of the steel tube. An extended parametric study is then carried out to identify the influence of the key parameters on the lateral impact behaviour of CFSTs with localised pitting corrosion. Finally, simplified design methods considering the features of pitting corrosion are proposed to predict the dynamic flexural capacity of locally pitted CFSTs subjected to lateral impact loads, and reasonable accuracy is obtained.

LiBr 수용액 내 부식억제제 농도에 따른 탄소강의 부식 깊이에 대한 통계적 분석

남영광(Young Kwang Nam),한상무(Sang Moo Han),유주현(Ju Hyun Yoo),정시영(Siyoung Jeong) 대한설비공학회 2019 대한설비공학회 학술발표대회논문집 Vol.2019 No.11

Carbon steel corrosion in high temperature(200℃) LiBr aqueous solutions used in the triple-effect absorption chillers is a very important topic. Although many studies were conducted, researches about the corrosion depth according to an inhibitor concentration have been rarely investigated. In this study, therefore, the effect of a concentration of the corrosion inhibitor Li2MoO4 on the corrosion depth under the high temperature operating conditions has been investigated. The depth of the pitting corrosion was measured using FE-SEM and analyzed using three statistical methods: General Lambda Distribution(GLD), Generalized Extreme Value(GEV), and Monte-Carlo Simulation. Also, a gravimetric method was used to the depth of the uniform corrosion. The results indicate that the corrosion depth are greatly reduced for both uniform and pitting corrosion if corrosion inhibitor is used. Moreover, the solution with a inhibitor concentration of 500ppm showed a smaller corrosion than the one with a concentration of 300ppm. The present study is expected to give useful information to for the development of tripple-effect absorption chillers using LiBr aqueous solution.

Case studies on the probabilistic characteristics of ultimate strength of stiffened panels with uniform and non-uniform localized corrosion subjected to uniaxial and biaxial thrust

Jinju Cui,Deyu Wang,Ning Ma 대한조선학회 2019 International Journal of Naval Architecture and Oc Vol.11 No.1

Based on Nonlinear Finite Element Analysis (NFEA), this paper focuses on the bi-axial ultimate strength of typical bottom structures under corrosion. On one hand, uniform and not simultaneous corrosion across different structures is introduced, and surrogate models by Gaussian Process (GP) are built for both longitudinal and transverse cases individually, and corresponding probabilistic characteristics are investigated; meanwhile, corrosion effects on interaction between bi-axial stresses at ultimate state are studied. On the other hand, non-uniform localized pitting corrosion of normally distributed circular shapes is introduced, and different pitting corrosion densities are considered; structural bi-axial ultimate strengths under pitting corrosion are studied, and the results are compared with that from equivalent uniform corrosion; the probabilistic characteristics of structural ultimate strength in life cycle are studied; finally, the ultimate strength under randomly distributed pitting corrosion is compared with results from normally distributed pitting and uniform corrosion under various boundary conditions.

Case studies on the probabilistic characteristics of ultimate strength of stiffened panels with uniform and non-uniform localized corrosion subjected to uniaxial and biaxial thrust

Cui, Jinju,Wang, Deyu,Ma, Ning The Society of Naval Architects of Korea 2019 International Journal of Naval Architecture and Oc Vol.11 No.1

Based on Nonlinear Finite Element Analysis (NFEA), this paper focuses on the bi-axial ultimate strength of typical bottom structures under corrosion. On one hand, uniform and not simultaneous corrosion across different structures is introduced, and surrogate models by Gaussian Process (GP) are built for both longitudinal and transverse cases individually, and corresponding probabilistic characteristics are investigated; meanwhile, corrosion effects on interaction between bi-axial stresses at ultimate state are studied. On the other hand, non-uniform localized pitting corrosion of normally distributed circular shapes is introduced, and different pitting corrosion densities are considered; structural bi-axial ultimate strengths under pitting corrosion are studied, and the results are compared with that from equivalent uniform corrosion; the probabilistic characteristics of structural ultimate strength in life cycle are studied; finally, the ultimate strength under randomly distributed pitting corrosion is compared with results from normally distributed pitting and uniform corrosion under various boundary conditions.

Pitting corrosion behavior in advanced high strength steels

Park, Il-Jeong,Lee, Sang-Min,Kang, Minwoo,Lee, Sukjin,Lee, Young-Kook Elsevier 2015 JOURNAL OF ALLOYS AND COMPOUNDS Vol.619 No.-

<P><B>Abstract</B></P> <P>The type and size of inclusions and their pitting corrosion behavior in dual-phase (DP), transformation-induced plasticity (TRIP), and twinning-induced plasticity (TWIP) steels were investigated. Whereas DP steel had single MnS inclusions, TRIP and TWIP steels had the complex inclusions of MnS and Al<SUB>2</SUB>O<SUB>3</SUB>, and MnS and Mn oxy-sulfide, respectively. TWIP steel had the most wide size distribution and the largest average size of inclusions. DP steel exhibited the lowest resistance to pitting corrosion due to the high density of inclusions. MnS inclusions in TRIP steel and Mn oxy-sulfide inclusions in TWIP steel acted as a galvanic anode in complex inclusions.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The density of inclusions was high in an order of DP, TWIP, and TRIP steels. </LI> <LI> TRIP and TWIP steels exhibited complex inclusions as well as single inclusions. </LI> <LI> DP steel had the lowest resistance to pitting corrosion. </LI> <LI> Initial pits occurred at the MnS particles of complex inclusions in TRIP steel. </LI> <LI> Initial pits formed at the Mn oxy-sulfide of complex inclusions in TWIP steel. </LI> </UL> </P>