**5. Summary**

372 Corrosion Resistance

Fig. 24. Scaled and cracked layer of corrosion products in 25Mn-3Si-1.5Al-Nb-Ti steel,

Fig. 25. Deep corrosion cracks in 25Mn-3Si-1.5Al-Nb-Ti steel after bending and the

Fig. 26. Microcracks running from non-metallic inclusions along hard martensitic plates in

25Mn-3Si-1.5Al-Nb-Ti steel, plastically deformed and immersed in 3.5wt% NaCl.

plastically deformed and immersed in 3.5wt% NaCl.

immersion in 3.5wt% NaCl.

The automotive industry still requires steel sheets with higher strength, ductility and technological formability. Recently, special pressure is put to the need of increasing the passive safety of passengers what can be met by using specially designed controlled crash zones absorbing the energy during crash events. High-manganese austenitic alloys satisfy these requirements. However, the main disadvantage is their relatively poor corrosion resistance.

The results presented in this study focused on the evaluation of corrosion resistance of two high-Mn steels of the different initial structure in acidic and chloride media. The investigations were carried out on the specimens after the thermo-mechanical rolling and after cold deformation. The results of immersion and potentiodynamic tests as well as structural analysis prove that both examined steels, independent of initial structure, have very low corrosion resistance in acidic medium and low corrosion resistance in chloride solution. In particular it was found that:


Corrosion Resistance of High-Mn Austenitic Steels for the Automotive Industry 375

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#### **6. Acknowledgement**

The author would like to thank to Dr. Wojciech Krukiewicz, Dr. Marek Opiela, Mr. Sławomir Kołodziej for carrying out some corrosion experiments and to Dr. Witold Walke for his fruitful discussion.

#### **7. References**


The corrosion resistance in chloride solutions in high-Mn alloys containing aluminum can be improved by the anodic passivation in 30% HNO3 aqueous solution (Hamada et al., 2005). It leads to the modification of the chemical composition of the surface layer, connected with reducing the manganese concentration at the surface layer and the enrichment this region in Al, improving the corrosion resistance. Another way of improving the corrosion resistance of high-manganese steels is to use zinc coatings. Due to alloying problems, the use of the electro-galvanizing process is promising (Hamada, 2007). The best solution seems to be the incorporation of Cr, which promotes the formation of a passivation layer and improves the corrosion resistance (Hamada, 2007; Mujica et al., 2010). However, the changes in SFE of austenite by Cr and the resulting main deformation mechanism should be taken into account. Some chemical composition strategies include alloys with increased nitrogen concentration, which improves the resistance to pitting corrosion (Mujica

The author would like to thank to Dr. Wojciech Krukiewicz, Dr. Marek Opiela, Mr. Sławomir Kołodziej for carrying out some corrosion experiments and to Dr. Witold Walke

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for his fruitful discussion.

13-25

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**7. References** 


**17** 

R. Rosliza

*Malaysia* 

*Kemaman, Terengganu,* 

**Improvement of Corrosion Resistance** 

*TATI University College, Jalan Panchor, Teluk Kalong,* 

**of Aluminium Alloy by Natural Products** 

Protection of metals from ever progressing corrosion presents one of the topical issues of this century. The increasing industrialization of our life is accompanied with the evergrowing number of metals that corrode and become devalued. Corrosion is a chemical or electrochemical reaction process against certain material, usually metal and its environment which produce the deterioration of the material and its properties. The corrosion reaction produces a less desirable material from the original metal and resulted in the reduced

Corrosion is a problem that impacts every industry. The serious consequences of the corrosion process have become a problem of worldwide significance. It is estimated that annual loss and damage due to corrosion in the United Kingdom costs about £5000 million; and approximately one tone of steel is lost through corrosion every 90 seconds. Further, it is estimated that 25% of this loss could be avoided by correct design, correct material selection

Even with the proper application of available countermeasures, the estimated cost by National Association of Corrosion Engineers (NACE) for replacing corroded piping systems in the United States alone stands well in excess of \$70 billion annually, which was 4.2% of the gross national product (GNP)-making corrosion one of the most potentially damaging

Even though the term of corrosion is usually applied to metals; all materials including ceramics, plastics, rubber and wood deteriorate at the surface to some extent as a result of being exposed to certain combinations of liquids and/or gases. Few practical examples are the rusting of tools and automobiles over many years of use; the failure of pipelines delivering volatile components such as natural gases and environmentally harmful chemicals such as crude oil and hydrochloric acid; bridge failure, ship failure (due to pumps, fuel tanks, boiler and sensors) and aircraft crashes; for example, Aloha Airlines flight 737 jet landing gear failure in 1988 (Radia, 2004). Therefore, the importance of understanding corrosion is clear, especially in the analysis and the design systems that incorporate metal as a major component material which exposed to corrosive environments.

losses to any commercial, private, or industrial property (Barbara and Robert, 2006).

function of a component or system, a significant problem encountered everyday.

and proper preventive processes (Barbara and Robert, 2006).

**1. Introduction** 

