METAL 2005 24.-26.5.2005, Hradec nad Moravicí

METAL 2005
24.-26.5.2005, Hradec nad Moravicí
___________________________________________________________________________
REVIEW OF CORROSION MITIGATION METHODS BY SURFACE
ENHANCEMENT OF METALS AND ALLOYS
Tadeusz Hryniewicz
Technical University of Koszalin, Racławicka 15-17, PL 75-620 Koszalin
E-mail: [email protected]
Abstract
The electrochemistry of corrosion proves the tendency for oxidation varies with the metal
and is related to its electrode potential. The structure and surface tension are characteristic
component features affecting the corrosion resistance of metallic materials. Surface finish has
long been known to have an impact on the life of a component in service. Most of metal
finishing processes, grinding, honing, lapping, and polishing produce a surface that is free of
defects such as gouges and scratches. It has been proved that the corrosion resistance of those
surfaces in corrosion environments is increased up to three times. Component surfaces are
usually in some state of residual stress. They can be in compression, tension, or stress free.
Residual stress has a direct impact on service life. It appears, residual stress has a greater
impact on service life than surface finish itself. It is especially important if a component
undergoes cyclic loading in service. To substantially improve the life of a component, it is
important to produce residual compressive stresses in a metallic component’s surface to
reduce tension during cyclic loading. Any tension may weaken the surface. Moreover, the
oscillating tension eventually causes damage at some points on the surface, usually at a flaw
or stress concentration such as a sharp corner or a fillet. These nucleation points may initiate
microcracks which develop and grow through the component until failure occurs. Once in
compression, the surface will experience much less tendency to fail during the loading cycle,
if any at all.
Surface enhancement methods are applied to a variety of metal components, beginning from
carbon steels, through low-alloy steels as well as aluminum components and others, e.g.
titanium alloys. Common corrosion rework practice in metallic components is to
mechanically remove corroded layers either by hand or by machining followed by a
mechanical surface enhancement treatment. The mechanical surface treatments are those the
most commonly used, like shot peening, and some new enhancement technologies being
developed quite recently, like laser shock peening (LSP), low plasticity burnishing (LPB), and
roller burnishing. While LSP is quite expensive to perform (finding its application for
titanium alloy specimens), low plasticity burnishing and roller burnishing demonstrate to
provide required depths and magnitudes of compressive residual stress. Moreover, these
methods of surface enhancement can induce a layer of compressive stress of sufficient
magnitude and depth into a pitted material. On this way one might prevent the formation of
fatigue cracking and/or significantly inhibit its growth.
An improved resistance to foreign object damage (FOD) is another important advantage of the
components after surface enhancement treatments. FOD ranges from a scratch or dent to a
deep gouge and is a major reason of fatigue crack nucleation in quickly moving machine
parts. Only the component surfaces in high compression can withstand the flaws.
The aim of the work is to review the present methods of mitigation and improvement of
corrosion resistance of steel component surfaces after selected ways of burnishing in
comparison with another surface treatments. Instead of typical Salt Fog Corrosion Exposure
tests, presented recently in many publications, the Electrochemical Impedance Spectrosopy
(EIS) investigation results are provided. They allow to present a semi-quantitative approach to
evaluate the corrosion rate and corrosion resistance of the studied metal surfaces.
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METAL 2005
24.-26.5.2005, Hradec nad Moravicí
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BIBLIOGRAPGY
1. Hryniewicz T., Corrosion resistance of coatings produced by combined surface
treatment, Seminar lecture, Mechanical Engineering Department of the Technological
Education Institute, Piraea, Greece, 2 March, 2001.
2. Hryniewicz T., Nykiel T., On the microcracks nucleation and growth in the technical
chromium layers coated electrolytically over the surface of heavy-duty machine parts,
Proc. of the METAL 2001 10th International Metallurgical and Materials Conference,
15-17 May, 2001, Hotel ATOM, Ostrava, Czech Republic, Symposium F: p.72, Paper
no. 192.
3. Hryniewicz T., Corrosion, Passivation, and Depassivation Problems, Seminar lecture,
Mechanical Engineering Department of the Technological Education Institute, Piraea,
Greece, 8 November, 2002.
4. Hryniewicz T., Rokosz K., The preliminary studies of corrosion resistance of steel
parts surface after burnishing, Proc. of 12th International Metallurgical & Materials
Conference METAL 2003, 20-22 May 2002, Hradec nad Moravici, Czech Republic,
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węglowych na ich odporność na korozję, Mater. 4 Konfer.Nauk. „Pomorska Inżynieria
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stali niskowęglowej, Mater. VII Konfer.Nauk.-Techn. Współczesne technologie w
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Conference. Chandler, AZ, 2000.
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METAL 2005
24.-26.5.2005, Hradec nad Moravicí
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15. Prevéy P.S., Shepard M.J., Smith P.R., The Effect of Low Plasticity Burnishing (LPB)
on the HCF Performance and FOD Resistance of TI-6Al-4V, Proc. of the 6th National
Turbine Engine High Cycle Fatigue (HCF) Conference, March 5-8, 2001,
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Burnishing, Proc. of 14th International Metallurgical & Materials Conference METAL
2005, 24-26 May 2005, Hradec nad Moravici, Czech Republic, Session D.
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