scholarly journals Methods to Calculate Corrosion Rates for Alloy 22 From Polarization Resistance Experiments

2006 ◽  
Author(s):  
Lana L. Wong ◽  
Sue I. Martin ◽  
Rau´l B. Rebak
Keyword(s):  
Corrosion Rate ◽  
Rapid Screening ◽  
General Corrosion ◽  
Absolute Value ◽  
Electrochemical Tests ◽  
Corrosion Rates ◽  
Alloy 22 ◽  
Fixed Set ◽  
Faraday Law ◽  
Current Potential

The general corrosion rate may be measured using immersion tests or electrochemical tests. The electrochemical tests are fast and can be used for a rapid screening of environmental effects such as temperature and electrolyte composition. The electrochemical tests are described in ASTM standards G 59 and G 102. The basis of these tests is to calculate the resistance to polarization (Rp) in a voltage vs. current plot and to convert these values to corrosion rates using the Faraday law. Commercial software can calculate the corrosion rate based on inputs from the operator. This paper discusses three ways of calculating the corrosion rate (Methods 1, 2 and 3) based on a fixed set of acquired data of voltage vs. current. The conclusions are that the way the corrosion rate is calculated does not impact greatly on the absolute value of the corrosion rate. Variations in the acquired data (current, potential) from one experiment to another seem more important that the manner the data is fitted with the Rp slope.

Effects of Fluoride and other Anions on the Corrosion of Alloy 22

2002 ◽  
Vol 757 ◽  
Author(s):  
A. L. Pulvirenti ◽  
K. M. Needham ◽  
M. A. Adel-Hadadi ◽  
A. Barkatt ◽  
C. R. Marks ◽  
...  
Keyword(s):  
Corrosion Rate ◽  
Phosphoric Acid ◽  
Corrosion Inhibitor ◽  
General Corrosion ◽  
Corrosion Resistant ◽  
Electrochemical Tests ◽  
Corrosion Rates ◽  
Reducing Conditions ◽  
Constant Ph ◽  
Alloy 22

ABSTRACTSamples of Alloy 22 were tested in solutions containing various anions in order to determine their effect on the corrosion of the alloy. It was found that Alloy 22 is relatively corrosion resistant in HCl and HNO3 at pH 1 and 160°C (general corrosion rates on the order of 10 μm/year), but more susceptible to phosphoric acid, especially under reducing conditions. The presence of fluoride raised the corrosion rate of Alloy 22 to the order 1 mm/year at pH 1, and fluoride is still active towards Alloy 22 at pH levels as high as 3.5. Samples tested in solutions of 1000xJ13 in which the pH was altered during testing showed an increase in corrosion rate over solutions of constant pH. Preliminary electrochemical tests suggest that nitrate may be an effective corrosion inhibitor in fluoride containing solutions, while sulfate is not.

Corrosion Behavior of Alloy 22 and Ti Grade 7 in a Nuclear Waste Repository Environment

CORROSION ◽  
2004 ◽  
Vol 60 (8) ◽  
pp. 764-777 ◽  
Author(s):  
F. Hua ◽  
G. Gordon
Keyword(s):  
Corrosion Rate ◽  
Corrosion Behavior ◽  
Nuclear Waste ◽  
Crevice Corrosion ◽  
Nuclear Waste Repository ◽  
General Corrosion ◽  
Corrosion Rates ◽  
Significant Difference ◽  
Alloy 22 ◽  
Waste Repository

Abstract Alloy 22 (UNS N06022) and Ti Grade 7 (UNS R52400) are the current corrosion-resistant materials of choice for fabricating the waste package outer barrier and the drip shield, respectively, for the proposed high-level nuclear waste repository at Yucca Mountain. In this work, the general and crevice corrosion behavior of annealed and welded Alloy 22 and Ti Grade 7 exposed in basic saturated water (BSW-12) for four and eight weeks at 60°C to 105°C were evaluated using the ASTM G78 method combined with surface analysis and statistical analysis of corrosion rate. The general corrosion rates for Alloy 22 and Ti Grade 7 were found to increase linearly with temperature but decrease with the exposure time. The mean corrosion rate was found to be 0.003 mpy (0.075 μm/y) at 60°C and 0.010 mpy (0.25μm/y) at 105°C for Alloy 22 and 0.008 mpy (0.20 μm/y) at 60°C and 0.022 mpy (0.56 μm/y) at 105°C for Ti Grade 7. No significant difference in corrosion behavior between the annealed and welded materials was observed. For both materials the surface imperfections inherited from materials processing did not seem to deteriorate the excellent corrosion resistance of the materials but might serve as the “traps” for corrosion products. The apparent activation energies for the temperature dependence of corrosion rates of Ti Grade 7 and Alloy 22 in BSW-12 environment were obtained as 25.3 (±5.5) KJ/mol and 23.7 (±4.5) KJ/mol, respectively. Although none of the materials was found susceptible to crevice corrosion under the test conditions, to conclude that these materials are immune to crevice corrosion in BSW-12 would require longer-term testing.

General Corrosion Behavior of N06022 in Super Concentrated Brines at Temperatures Higher than 100°C

2008 ◽  
Vol 1124 ◽  
Author(s):  
Raul B. Rebak
Keyword(s):  
Corrosion Resistance ◽  
Corrosion Behavior ◽  
Localized Corrosion ◽  
General Corrosion ◽  
Short Term ◽  
Corrosion Resistant ◽  
Electrochemical Tests ◽  
Alloy 22 ◽  
Nickel Based Alloy ◽  
Anions And Cations

AbstractAlloy 22 (N06022) is a highly corrosion resistant nickel based alloy. Extensive research has been conducted in the last eight years on the corrosion behavior of Alloy 22, mainly regarding its resistance to localized corrosion. Less attention has been paid to the general corrosion resistance in highly concentrated brines that may result from the deliquescence of salts contained in dust. Salts such as mixtures of NaCl, KCl, CaCl2, NaNO3, and KNO3 may deliquesce at temperatures above 100°C through absorption of moisture from the air. Electrochemical tests were used to assess the general corrosion behavior of Alloy 22 in brines with chloride and nitrate concentrations ranging from 8 molal to 100 molal in the temperature range 100 to 160°C. The effect of mixed anions and cations was also studied. Results show that, even for short-term immersion periods, the corrosion rate of Alloy 22 in high temperatures super concentrated brines is generally below 10 μm/year.

The Corrosion Behavior of Niobium in Hydrochloric Acid Solutions

CORROSION ◽  
1980 ◽  
Vol 36 (10) ◽  
pp. 554-558 ◽  
Author(s):  
B. S. COVINO ◽  
J. P. CARTER ◽  
S. D. CRAMER
Keyword(s):  
Hydrochloric Acid ◽  
Corrosion Rate ◽  
Corrosion Behavior ◽  
Mineral Resources ◽  
The United States ◽  
General Corrosion ◽  
Ferric Ion ◽  
Acid Solutions ◽  
Corrosion Rates ◽  
Hydrochloric Acid Solutions

Abstract Studies to better understand the corrosion behavior of niobium in hydrochloric acid solutions have been conducted as part of the Bureau of Mines’ effort to conserve the United States’ mineral resources. A study of the general corrosion behavior of niobium as a function of acid concentration, time, oxygen, and added ferric ion is reported. Weight loss (corrosion) tests were performed in air saturated (agitated and static) and helium saturated (agitated) hydrochloric acid solutions ranging from 1N to 10N at temperatures from 35 to 100 C and exposures up to 60 days. The 30 day corrosion rates ranged from 0.0 μm/y in 35 C air saturated (agitated) 1N HCl to 230 μm/y in air saturated (static) 9.8N HCl at 85 C. Although the corrosion rates decreased rapidly for times up to 30 days, the rates for 30 and 60 days were essentially identical. The presence of air did not affect the corrosion rate of niobium, while the presence of only 70 ppm of ferric ion reduced the corrosion rate in most air saturated 5N and 10N HCl solutions.

scholarly journals Long-Term Corrosion Behavior of Alloy 22 in 5 M CaCl2 at 120°C

2006 ◽  
Author(s):  
John C. Estill ◽  
Gary A. Hust ◽  
Kenneth J. Evans ◽  
Marshall L. Stuart ◽  
Rau´l B. Rebak
Keyword(s):  
Corrosion Rate ◽  
Salt Concentration ◽  
Crevice Corrosion ◽  
Immersion Time ◽  
Corrosion Potential ◽  
Open Circuit ◽  
General Corrosion ◽  
Critical Potential ◽  
Alloy 22

In conditions where tight crevices exist in hot chloride containing solutions Alloy 22 may suffer crevice corrosion. The occurrence (or not) of crevice corrosion in a given environment (e.g. salt concentration and temperature), is governed by the values of the critical potential (Ecrit) for crevice corrosion and the corrosion potential (Ecorr). This paper discusses the evolution of Ecorr and corrosion rate (CR) of creviced Alloy 22 specimens in 5 M calcium chloride (CaCl2) at 120°C. Tested specimens included non-creviced rods and multiple creviced assemblies (MCA) both non-welded (wrought) and welded. Results show that Alloy 22 suffers crevice corrosion under the open circuit conditions in the aerated hot CaCl2 brine. However, after more than a year immersion the propagation of crevice corrosion was not significant. The general corrosion rate decreased or remained unchanged as the immersion time increased. For rods and MCA specimens, the corrosion rate was lower than 100 nm/year after more than a year immersion time.

scholarly journals Review of Corrosion Modes For Alloy 22 Regarding Lifetime Expectancy of Nuclear Waste Containers

2002 ◽  
Vol 757 ◽  
Author(s):  
Raúl B. Rebak ◽  
John C. Estill
Keyword(s):  
Corrosion Rate ◽  
Nuclear Waste ◽  
Outer Layer ◽  
Localized Corrosion ◽  
General Corrosion ◽  
Corrosion Resistant ◽  
Waste Package ◽  
Environmentally Assisted Cracking ◽  
Alloy 22 ◽  
Lifetime Expectancy

ABSTRACTAlloy 22 (UNS N06022) was selected to fabricate the corrosion resistant outer barrier of a two-layer nuclear waste package container. This paper reviews the main corrosion degradation modes that are predicted for the outer layer of the container. Current results show that the containers would perform well under general corrosion, localized corrosion and environmentally assisted cracking (EAC). For example, the general corrosion rate is expected to be below 100 nm/year and the container is predicted to be outside the range of potential for localized corrosion and environmentally assisted cracking.

Corrosion Problems in Sugar Factories in Mauritius

2011 ◽  
Vol 110-116 ◽  
pp. 1983-1989
Author(s):  
L. Tengur ◽  
B.Y.R. Surnam
Keyword(s):  
Corrosion Rate ◽  
Sugar Cane ◽  
Low Carbon Steel ◽  
Extraction Process ◽  
Low Carbon ◽  
Stainless Steel 316L ◽  
Electrochemical Tests ◽  
Corrosion Rates ◽  
Juice Extraction ◽  
The Cost

In Mauritius, corrosion costs forms a large part of the expenses of sugar cane mills and presently there has not been any study on this issue. The present study was therefore performed at one of the sugar cane mills in Mauritius so as to identify the different modes of corrosion degradation and the corrosivity of commonly used metals with respect to the corrosive fluids (mainly juices) encountered in the juice extraction process. The cost associated with the corrosion degradation was eventually calculated. Electrochemical tests were performed to measure and compare the corrosion rate for the metals in the corrosive fluids. It was observed that the highest and the lowest corrosion rates were recorded for pre-extractor mill juice and syrup respectively. Low carbon steel generally had the fastest corrosion rate while stainless steel 316L corroded the least. Finally, from gathered data, the cost of corrosion was found to be 6.6% of the turnover of the factory.

Possible Missing Link in CO2 Corrosion Prediction

2021 ◽  
Author(s):  
Yves Gunaltun
Keyword(s):  
Corrosion Rate ◽  
Field Experience ◽  
Prediction Models ◽  
Co2 Corrosion ◽  
Corrosion Mechanism ◽  
General Corrosion ◽  
Flat Bottom ◽  
Research Results ◽  
Corrosion Rates ◽  
The Impact

Abstract CO2 corrosion prediction models predict a general corrosion rate, but field failures are due to localised CO2 corrosion. That is why predicted corrosion rates are correlated to a corrosivity level. These models generally consider that the corrosion rate remains, after the initiation period, unchanged as long as operating and/or production parameters remain unchanged. However, 25 years of field experience and also some recent research results confirmed that after an initial phase of high corrosion rates, the CO2 corrosion rates may significantly decrease with time forming flat-bottom large corrosion features (mesa corrosion) and stabilise. Depending on the corrosivity level the time needed for the stabilisation would be up to about 12 months. To be noted that the stabilization has been known since 2003-2004. It was first used in 2005 for the development of two gas fields with success. In 2008, it was used for the prediction of the remaining life of gas pipelines transporting very corrosive wet gas. The use of costly CRA / cladded pipes was avoided. Gunaltun Y. and call. made the first publication about the importance of the stabilization on the remaining pipeline service life in 2009. Then, possible mechanisms of stabilization were published by Gunaltun Y. in 2012 and Gunaltun Y. and call. 2013. In the present paper the field experience, the research results and the mechanisms leading to stabilisation are discussed in detail and summarised. The main driving force is the galvanic action between anodic and cathodic zones. The clustering of corrosion features completes the process of stabilisation. Re-initiation of corrosion, after stabilisation, has not been observed neither in the laboratory nor in field. The reasons why stabilisation is a non-reversible process are also explained in detail. The conclusions are integrated in the general understanding of CO2 corrosion mechanism. Then a new method is proposed to complete the corrosion prediction approaches used by the industry. Even though some research is still needed to validate the impact of some parameters involved in the stabilisation process, the stabilisation concept is now mature enough for including it in the prediction models. It is very likely that stabilisation is one of the missing links in CO2 corrosion prediction chain.

The Stern-Geary and related methods for determining corrosion rates

1975 ◽  
Vol 28 (2) ◽  
pp. 243 ◽  
Author(s):  
DB Matthews
Keyword(s):  
Corrosion Rate ◽  
Corrosion Potential ◽  
Transfer Coefficients ◽  
Corrosion Rates ◽  
Linear Current ◽  
Reversible Potential ◽  
Special Cases ◽  
The Difference ◽  
Current Potential

Calculation of the current-potential relations for corroding electrodes as a function of the cathodic and anodic transfer coefficients and as a function of the difference between the corrosion and reversible potentials demonstrates the deficiencies of the Stern-Geary equation for determining corrosion rates. The calculations also demonstrate that a linear current-potential relation is not predicted except over very small ranges of potential, e.g. 2 mV. As a consequence, it is essential in using the Stern- Geary and related methods to determine the slope dE/di at the corrosion potential. The Stern-Geary method is not applicable for systems where the corrosion potential is close to the reversible potential for either of the participating reactions and fortuitous linearity of currentvoltage plots may be erroneously interpreted as indicating that the Stern-Geary method is applicable. Methods of determining the corrosion rate which depend upon measuring the difference ΔE in corrosion and reversible potentials are not likely to be successful because of their sensitivity to the value of ΔE. A new derivation of the slope dE/di at the corrosion potential is presented and it is shown that the Stern-Geary and Mansfeld-Oldham equations may be derived as special cases. This new derivation is not immediately useful for determining the corrosion rate but it is shown that by measuring the dependence of the corrosion potential on concentration of cathodic reactant then the new derivation can be useful for rapid and accurate corrosion rate measurements even for small values of ΔE.

scholarly journals Effect of Small Variation in the Composition of Plates and Weld Filler Wires on the General Corrosion Rate of Ni-Cr-Mo Alloys

2005 ◽  
Author(s):  
David V. Fix ◽  
John C. Estill ◽  
Rau´l B. Rebak
Keyword(s):  
Corrosion Rate ◽  
Filler Metal ◽  
Small Variation ◽  
Weight Percent ◽  
General Corrosion ◽  
Nickel Chromium ◽  
Immersion Corrosion ◽  
Heat Treated ◽  
Alloy 22 ◽  
G 28

The ASTM standard B 575 provides the requirements for the chemical composition of Nickel-Chromium-Molybdenum (Ni-Cr-Mo) alloys such as Alloy 22 (N06022) and Alloy 686 (N06686). The compositions of each element are given in a range. For example, the content of Mo is specified from 12.5 to 14.5 weight percent for Alloy 22 and from 15.0 to 17.0 weight percent for Alloy 686. It was important to determine how the corrosion rate of welded plates of Alloy 22 using Alloy 686 weld filler metal would change if heats of these alloys were prepared using several variations in the composition of the elements even though still in the range specified in B 575. All the material used in this report were especially prepared at Allegheny Ludlum Co. Seven heats of plate were welded with seven heats of wire. Immersion corrosion tests were conducted in a boiling solution of sulfuric acid plus ferric sulfate (ASTM G 28 A) using both as-welded (ASW) coupons and solution heat-treated (SHT) coupons. Results show that the corrosion rate was not affected by the chemistry of the materials within the range of the standards.

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