Grain refinement is known to lead to improvements in strength and wear resistance. Inherent processing involved in grain refinement alter both the bulk and the surface of a material, leading to changes in grain boundary density, orientation, and residual stress. Ultimately, these surface changes can have an impact on electrochemical behavior and, consequently, corrosion susceptibility as evidenced by the large number of studies on the effect of grain size on corrosion, which span a range of materials and test environments. However, there has been limited work on developing a fundamental understanding of how grain refinement and more generally how grain size affects the corrosion resistance of an alloy. Existing literature is often contradictory, even within the same alloy class, and a coherent understanding of how grain size influences corrosion response is largely lacking. A survey of previous work related to the relationship between grain size and corrosion resistance for a number of light meta...

Effect of Grain Size on Corrosion: A Review

Corrosion is a subject of interest to interdisciplinary research communities, combining fields of materials science, chemistry, physics, metallurgy and chemical engineering. In order to understand mechanisms of corrosion and the function of corrosion inhibitors, the reactions at the interfaces between the corrosive electrolyte and a steel surface, particularly at the initial stages of the corrosion process, need to be described. Naturally, these reactions are strongly affected by the nature and properties of the steel surfaces. It is however seen that the majority of recent corrosion and corrosion-inhibition investigations are limited to electrochemical testing, with ex situ analysis of the treated steels (post-exposure analysis). The characterization of materials and their surface properties, such as texture and morphology, are not being considered in most studies. Similarly, in situ investigations of the initial stages of the corrosion reactions using advanced surface characterization techniques are scarce. In this review, attention is brought to the importance of surface features of carbon steels, such as texture and surface energy, along with defects dislocation related to mechanical processing of carbon steels. This work is extended to a critical review of surface analytical techniques used for characterization of carbon steels in corrosive media with particular focus on examining steel surfaces treated with corrosion inhibitors. Further, emerging surface analysis techniques and their applicability to analyse carbon steels in corrosive media are discussed. The importance of surface properties is commonly addressed by surface scientists as well as researchers in other chemistry fields such as nanotechnology, fuel cells, and catalysis. This article is expected to appeal to a broad scientific community, including but not limited to corrosion scientists, material chemists, analytical chemists, metal physicists, corrosion and materials engineers.

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Carbon steel corrosion: a review of key surface properties and characterization methods

The influence of nanocrystalline structure and processing route on corrosion of stainless steel: A review

The importance of application of shot peening process to obtain nanocrystal surface is presented with an inclusive clarification of actual state of the art. Description of different shot peening methods which have proved to be able to create nanocrystallised layers is presented. Then the available microstructural characteristics of nanocrystal thin layers obtained with different processes are depicted. In addition, the influence of the process is reviewed on material behaviour under different loading conditions. On this basis, some possible addresses for future research in this field are drawn and underlined.

Review of shot peening processes to obtain nanocrystalline surfaces in metal alloys

A nanocrystalline surface layer was produced on an AISI-321 stainless steel by severe plastic deformation via ultrasonic peening (UP). The microstructural evolution of the surface layer was characterized by means of X-ray diffraction (XRD) analysis and transmission electron microscopy (TEM). The volume fraction of strain-induced α-martensite as a function of the effective strain ( e ¯ ) was evaluated quantitatively using XRD and magnetic measurements. Considering the e ¯ magnitudes and the TEM data obtained, it is concluded that a grain refinement of austenitic structure passes ahead of the α-martensite formation, particularly in the top surface layer. The nanocrystalline austenitic grain structure (mean grain size ∼ 15 nm) was observed at e ¯ = 0.45 , while the startup of the strain-induced martensitic transformation was revealed at the strain extent of 0.62. The nanostructured surface layer formed after straining to e ¯ = 0.8 already contains mainly the martensite nanograins characterized by an average size of about 10 nm. Grain size increased gradually up to 60 nm within the layer containing both austenite and martensite phases at a depth of about 30 μm from the treated surface. Both the microhardness behavior of the stainless steel surface and its corrosion performance in 3.5% NaCl solution can be enhanced by the UP. They are shown to be in correlation with: (i) the grain refinement process and (ii) the increase in the volume fraction of strain-induced α-martensite.

X.Y. Wang

Papers

Mechanical, electrochemical and tribological properties of nano-crystalline surface of 304 stainless steel

Wear and corrosion wear of medium carbon steel and 304 stainless steel

Application of an electrochemical scratch technique to evaluate contributions of mechanical and electrochemical attacks to corrosive wear of materials

The effect of wear and corrosion on internal crystalline texture of carbon steel and stainless steel