Simulating and Understanding Localized Corrosion of Stainless Steels

This report investigates the critical issue of localized corrosion in additive manufactured stainless steels, a significant concern across various industries including oil, water pumps, and pipelines. The study emphasizes the combined effects of corrosion, erosion, and wear on metal deterioration, and the role of protective inert films. The research employs Finite Element (FE) models, including upper-bond methods and slip-line theory, and explores Micro-Scale Dynamical Models (MSDM) to simulate wear processes. The methodology includes analyzing the application of stainless steel in additive manufacturing, identifying the sources of localized corrosion, and characterizing the chemical and mechanical properties of the steel. It also covers the implementation of MSDM to simulate wear, the use of duplex stainless steels, and the application of Selective Laser Melting (SLM). The report provides a comparative analysis of different FE model results and a detailed literature review of previous research. The goal is to understand the growth of inert films and their impact on corrosion and wear, along with the influence of mechanical properties on corrosive wear. The study utilizes computational tools and numerical equations to develop FE models for simulation, with potential application of WebCorr's corrosion prediction software.

Simulating and Understanding Localized
Corrosion of Additive Manufactured
Stainless Steels Under Simulated Pipeline
Mechanical, Corrosion and Erosion
Conditions

Introduction
a) Stainless steel has been extensively used in many manufacturing industries for
decades, like steel components in oil refining facilities, chemical factories,
mineral transport systems and water-cycle pumps and most importantly
pipelines.
b) The Stainless steel which is resisted from the corrosion can provide extreme
conditions with erosion and impact of elements.
c) It has been observed that the combined effect of corrosive erosion and wear
could bring deterioration on metal much higher than of the damage created by
corrosion or wear individually.
d) The prompt passivation practice of stainless steel may avoid the steel from
severe damage through minimizing the combined effect of corrosion and
erosion due to the establishment of a shielding inert film on the surface. Once
the inert film is cracked by the effect of sand elements or other types of wear,
the metal may restore a new inert film on the simple surface in about one tenth
second (Wang and Li (2002), Garcia et al. (2001)).

Problem Statement
As the combined effect of corrosion and erosion may lead to the sever
damage on the stainless steel meatal materials, the investigations of
chemical and mechanical properties are required based on the Newton’s
law. Though various FE models are developed to analyze the wear
processes utilizing different methods, such as upper-bond method, the
finite element method, slip line theory and the molecular dynamics
simulation, very limited research have been carried out to get rid off
corrosion and erosion synergy on material properties.

Deliverables
1) Clear visualization of the localized corrosion causes the several
problem in various industries such as oil, water pump and
pipeline etc.
2) Different FE model to simulate the corrosive wear activities i.e.,
upper-bond method, slip line theory and the finite element
method.
3) Comparison of all mentioned FE results.
4) Micro-scale dynamic method (MSDM) to analyze the corrosion
effect on the stainless steel

Literature Review
1. Lia et al. (1999) have demonstrated a Micro Scale Dynamical Model to
analyze the wear process and material performance durability.
2. Li and Chen (2003) utilized the MSDM to simulate the corrosion and
erosion of metal materials based on the Newton’s Law and fundamental
materials mechanical properties.
3. Li and Zhang (2001) studied the synergy of corrosion and mechanical
scratch after self healing inert film of stainless steel. Also the failure of
inert film was investigated using a using a micro-mechanical probe.
4. Li et al. (2009) have developed a computational model to analyze the
metastable pit growth of stainless steel and its transition to make it
stable.

Proposed Methodology
 Application of Stainless Steel in Additive Manufacturing: This metal
possesses high yield strength and toughness which make it most usage
metal poder in Additive Manufacturing.
 Source of localized corrosion development within the metals: This is the
type of corrosion while the localized area of metal surface attacked. This is
mainly occured due to the heterogeneities within the material or exposion
of the material to the environment.
 Characterization of chemical and mechanical properties of Stainless Steel:
It includes the grain size of the metal, microstructure morphology and
inclusion content. Also systematic evaluation of porosity distribution.

..Contd...
 Implementation of Micro Scale Dynamical Model (MSDM) to simulate
various wear processes: In this model the material system is to be
discretized by lattice.
 Duplex Stainless steel (DSSs): These are corrosion resistance alloys widely
applicable in truculent environment. Steel alloy with addition 2.7-3.3%Cu
gives the DSSs.
 Selective Laser Melting (SLM): This technology acquire Steel passive film
to produce metal powders by laser melting of successive layers.
 Understanding the growth of inert film:
 The impact of inert film over corrosion and wear
 The impact of mechanical properties of inert film over corrosive wear

Required Resources
To carryout the present research work and to achieve the main objective
following al the mentioned proposed methodology the mathematical
numerical equations are to be formulated i.e., lattice site, total force of the site
, etc.
To develope the FE model for numerical simulation WebCorr's corrosion
prediction software can be utilized.

Summary
The application of stainless steel in Manufacturing industry has been
increased for decades. Beside this application localized corrosion
formation is the major problem to be recognized. The experimental
investigation has been performed to understand the mechanical and
chemical properties of the inert film, which detach the substratum
materials from the adjacent corrosive blend. In this research work
various FE model have been developed to analyze corrosion-erosion of
Stainless Steel materials.

References
Wang, X.Y. and Li, D.Y., 2002. Mechanical and electrochemical behavior of
nanocrystalline surface of 304 stainless steel. Electrochimica Acta, 47(24), pp.3939-
3947.
Garcıa, I., Drees, D. and Celis, J.P., 2001. Corrosion-wear of passivating materials in
sliding contacts based on a concept of active wear track area. Wear, 249(5-6),
pp.452-460.
Li, D.Y., Elalem, K., Anderson, M.J. and Chiovelli, S., 1999. A microscale
dynamical model for wear simulation. Wear, 225, pp.380-386.
Chen, Q. and Li, D.Y., 2003. Computer simulation of solid particle
erosion. Wear, 254(3-4), pp.203-210.
Zhang, T. and Li, D.Y., 2001. Improvement in the corrosion-erosion resistance of
304 stainless steel with alloyed yttrium. Journal of materials science, 36(14),
pp.3479-3486.
Li, L., Li, X., Dong, C. and Huang, Y., 2009. Computational simulation of
metastable pitting of stainless steel. Electrochimica Acta, 54(26), pp.6389-6395.

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