Effect of Pitting Corrosion on Strength of AISI 410 Stainless Steel Compressor Blades

2014 ◽  
Vol 606 ◽  
pp. 227-231 ◽  
Author(s):  
Mazmir Mat Noh ◽  
Farzin Mozafari ◽  
Muhammad Adil Khattak ◽  
Mohd Nasir Tamin
Keyword(s):  
Stainless Steel ◽  
Pitting Corrosion ◽  
Tensile Specimen ◽  
Maximum Diameter ◽  
Compressor Blades ◽  
Strength Tests ◽  
Corrosion Pits ◽  
Pit Depth ◽  
Geometry Analysis ◽  
Nucleation Phenomenon

In the present paper, effects of pitting corrosion on the strength of members made of AISI 410 Martensitic stainless steel were investigated. Stainless steel compressor blades in power generation industries commonly suffer from pitting corrosion. Pits geometry analysis and strength tests have been conducted. Pits geometry analysis established the maximum pit depth of 0.26 mm along with the maximum diameter of 1 mm. In addition, strength and elongation of the pitted tensile specimen gradually decrease with the increase of the area lost due to pitting corrosion. A damage nucleation phenomenon at the initial load values is also postulated.

EFFECT OF ARTIFICIALLY PRODUCED PIT-LIKE DEFECTS ON THE STRENGTH OF AISI 410 STAINLESS STEEL COMPRESSOR BLADES

2016 ◽  
Vol 78 (6-11) ◽  
Author(s):  
M. A. Khattak ◽  
Mazmir Mat Noh ◽  
M. N. Tamin ◽  
Nida Iqbal ◽  
Amir Husni Muhd Syariff ◽  
...  
Keyword(s):  
Power Generation ◽  
Stainless Steel ◽  
Yield Strength ◽  
Pitting Corrosion ◽  
Martensitic Stainless Steel ◽  
Tensile Specimen ◽  
Compressor Blades ◽  
Steel Microstructure ◽  
Strength Tests ◽  
Structure Strength

In the present paper, the effect of artificially produced pit-like defects on the strength of members made of AISI 410 martensitic stainless steel were investigated. Compressor blades in power generation industries made of AISI 410 stainless steel commonly suffer from pitting corrosion. Well-defined pit-like defects were artificially produced on various specimen and strength tests were conducted. AISI 410 stainless steel microstructure shows a typical body-centered tetragonal (bct) structure. Strength tests analysis established yield strength of 547 MPa for Case 1 (max depth-max diameter) whereas a yield strength of 585 MPa for Case 2 (min depth-min diameter). In addition, strength and elongation of the artificially produced pitted tensile specimen gradually decrease with the increase of the area lost due to artificially produced pits.  

Modeling the Influence of Microstructure on Stress Distributions and Concentrations in Pitting Corrosion

2018 ◽  
Author(s):  
Patrick Brewick ◽  
Andrew Geltmacher ◽  
Siddiq M. Qidwai
Keyword(s):  
Stainless Steel ◽  
Pitting Corrosion ◽  
Mechanical Load ◽  
High Strength ◽  
Geometrical Shape ◽  
Stress Distributions ◽  
Concentration Factors ◽  
Corrosion Pit ◽  
Stress Concentration Factors ◽  
Corrosion Pits

Despite the many advances made in material science, stainless steel and aluminum remain the structural materials best-suited for the naval fleet. While these metallic materials offer many benefits, such as high strength and good toughness, their persistent exposure to the maritime environment inevitably leads to issues with corrosion. Among the various manifestations of corrosion, pitting corrosion is of particular concern because the transition of corrosion pits to stress-corrosion cracks can lead to catastrophic failures. Traditional pitting corrosion analyses treat the pit shape as a semi-circle or ellipse and typically assume a growth pattern that maintains the original geometrical shape. However, when the underlying microstructure is incorporated into the model, pit growth is related to the grains surrounding the pit perimeter and the growth rate is proportional to crystallographic orientation. Since each grain has a potentially different orientation, pit growth happens at non-uniform rates leading to irregular geometries, i.e., non-circular and non-elliptical. These irregular pit geometries can further lead to higher stresses. This work presents a detailed look at corrosion pit growth coupled with mechanical load through a numerical model of a two-dimensional stable corrosion pit. Real microstructural information from a sample of 316 stainless steel is incorporated into the model to analyze microstructural effects on pit growth. Through this work, stress distributions and stress concentration factors are examined for a variety of pit geometries, including comparisons of their range of values to a typical, semi-circular pit. The consequences of these stress distributions and concentration factors are discussed.

Collaboration solves long standing corrosion problem

2020 ◽  
Vol 60 (2) ◽  
pp. 598
Author(s):  
M. Brameld ◽  
S. Thomas ◽  
G. S. Malab
Keyword(s):  
Stainless Steel ◽  
Pitting Corrosion ◽  
Ct Scanning ◽  
Test Program ◽  
Corrosion Reaction ◽  
Impervious Layer ◽  
Steel Equipment ◽  
Corrosion Problem ◽  
External Corrosion ◽  
Corrosion Pits

External pitting corrosion has been a long standing issue for stainless steel pressure equipment systems on Woodside offshore facilities. Experience has shown that this pitting cannot be effectively managed by inspection and, as a result, the current policy is that piping replacement should be planned once the presence of significant pitting corrosion has been identified. All Woodside offshore facilities have 316-grade stainless steel pressure equipment which is experiencing active external corrosion pitting to varying degrees. This represents the potential for hundreds of millions of dollars in piping replacement across the company. STOPAQ is an established product for the mitigation of external corrosion in carbon steel equipment however, it has not previously been used at Woodside on stainless steel equipment to address pitting corrosion. Through collaboration with the Woodside Future Laboratory at Monash University, Materials and Corrosion Engineering, Woodside Energy Limited has challenged the old established theory regarding the mechanism of pitting in stainless steel and a test program has been devised to validate the new way of thinking, which postulates that elimination of moisture and oxygen from the pits, by the application of an impervious layer like STOPAQ, will stifle the corrosion reaction and arrest the pitting. A recently completed test program at Monash which utilised computed tomography (CT) scanning, to very accurately determine the volume of corrosion pits, has confirmed that the application of STOPAQ to pitted stainless steel is very effective at mitigating this type of corrosion.

Notes on a System For Rating Pitting Corrosion

CORROSION ◽  
1955 ◽  
Vol 11 (1) ◽  
pp. 50-52 ◽  
Author(s):  
RUSSELL W. HENKE
Keyword(s):  
Metal Surface ◽  
Pitting Corrosion ◽  
Finite Dimension ◽  
Equivalent Diameter ◽  
Digit Number ◽  
Principal Characteristics ◽  
Standard Interval ◽  
Corrosion Pits ◽  
Pit Depth ◽  
Surface Nature

Abstract A system is proposed for describing corrosion pits in a metal surface by a combination of agglutinated numbers and letters coded to a schedule rating the five principal characteristics of pitting corrosion. The system would facilitate transmission of pitting data by providing a 10-digit number covering their depth, equivalent diameter (including those of irregular shape), area (expressed as a percentage of total surface), nature of pit walls and time (reduced to a standard interval). Pit depth is expressed as a percentage of material thickness rather than a finite dimension, walls would be rated vertical or gradual in comparison with a 45 degree angle and time would be in penetration per year. Area of pits as percentage of total area would be determined by placing over the pitted surface a transparent grid and comparing the area visually with a conventional standard delineating 10 stages of severity. Suggestions and recommendations for improvement of the system and submission of specimens of pitted material are solicited by the author.

Metastable pitting corrosion of stainless steel and the transition to stability

1992 ◽  
Vol 341 (1662) ◽  
pp. 531-559 ◽  
Keyword(s):  
Stainless Steel ◽  
Current Density ◽  
Electrode Potential ◽  
Chloride Solution ◽  
Critical Value ◽  
Nucleation Site ◽  
Pit Nucleation ◽  
Stable Growth ◽  
Corrosion Pits ◽  
Pit Depth

The evolution of corrosion pits on stainless steel immersed in chloride solution occurs in three distinct stages: nucleation, metastable growth and stable growth. This paper describes the growth of metastable corrosion pits on stainless steel immersed in chloride solution, and their transition to stability. The rate of growth of individual corrosion pits is controlled by diffusion of the dissolving metal cations from the pit interior, the surface of which is saturated with the metal chloride. This process is independent of electrode potential. Analysis of the diffusion yields a critical value of the product of the pit radius and its dissolution current density (termed the ‘pit stability product’) below which the pit is metastable and may repassivate, and above which the pit is stable. The critical value of the pit stability product for stainless steel in chloride solution is 0.3 A m -1 . All pits, whether metastable, or destined to become stable, grow initially in the metastable condition, with a pit stability product which increases linearly with time, but below the critical value. Metastable growth requires a perforated cover over the pit mouth to provide an additional barrier to diffusion, enabling the aggressive pit anolyte to be maintained. In this state pits grow at a constant mean current density which is maintained by periodic partial rupture of the cover. Stable pit growth is then achieved when the cover is no longer required for continued propagation, and the pit depth is itself a sufficient diffusion barrier; stability is characterized by a constant mean pit stability product above the critical value. If the cover is lost prematurely, before the critical pit stability product is achieved, the pit anolyte is diluted and repassivation is inevitable. In contrast to the growth rate of individual pits, the distribution of pitting current transients is dependent on electrode potential: the pit nucleation site, particularly its geometry, is exclusively responsible for this potential distribution. It is proposed th at shallower, more-open sites are activated only at higher potential and higher current density, and are consequently more likely to achieve stability.

NIROSTA 4429

Alloy Digest ◽  
2000 ◽  
Vol 49 (5) ◽  
Keyword(s):  
Stainless Steel ◽  
Corrosion Resistance ◽  
High Temperature ◽  
Pitting Corrosion ◽  
Intergranular Corrosion ◽  
Heat Treating ◽  
Low Carbon ◽  
High Nitrogen ◽  
Temperature Performance ◽  
Pitting Corrosion Resistance

Abstract Nirosta 4429 is a low-carbon, high-nitrogen version of type 316 stainless steel. The low carbon imparts intergranular corrosion resistance while the nitrogen imparts both higher strength and some increased pitting corrosion resistance. It is recommended for use as welded parts that need not or cannot be annealed after welding. This datasheet provides information on composition, physical properties, elasticity, and tensile properties. It also includes information on high temperature performance and corrosion resistance as well as forming, heat treating, and joining. Filing Code: SS-787. Producer or source: ThyssenKrupp Nirosta.

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