The session was moderated by PASSAD Secretary General Dr. Erdem Şireli and featured Prof. Dr. Hüseyin Çimenoğlu, faculty member of the Metallurgical and Materials Engineering Department at Istanbul Technical University (ITU), as a panelist.
Şireli: “Cost Is Not the Initial Investment, but the Impact Created Throughout the Entire Service Life”
Opening the session, Moderator Dr. Erdem Şireli emphasized that evaluating operating costs in industrial applications solely based on the initial investment cost is an incomplete approach. Şireli stated that cost analyses should take into account wear, corrosion, maintenance and repair expenses, as well as potential production losses that may arise throughout the material’s service life.
Şireli noted that stainless steel forms a self-renewing passive layer on its surface, and that this feature provides corrosion resistance while directly reducing long-term operating costs. He added: “Stainless steel is not miraculous under all conditions; if the correct alloy is not selected and environmental analysis is not carried out properly, the expected performance cannot be achieved. At this point, the right engineering approach is just as critical as material selection.”
“95% of Metals in the World Are Iron Based”
Beginning his speech by recalling that ITU is celebrating its 253rd anniversary and that Türkiye’s first Metallurgical Engineering department was established within the ITU Faculty of Mines in 1961, Prof. Dr. Hüseyin Çimenoğlu stated that steel accounts for a USD 1.5 trillion share in global trade and that 95% of metals produced worldwide are iron based.
Çimenoğlu noted that there are more than 3,500 steel grades used in industry and that 52% of steel is utilized as structural steel in the building and infrastructure sectors. He explained that the first structures using steel as a skeleton were erected in Chicago and New York in 1883, while the Brooklyn Bridge, completed in the same year, became the first major steel bridge. He also cited Beijing National Stadium (“Bird’s Nest”), which used 42,000 tons of steel, as one of the important examples in this field. Referring to the sinking of the Titanic, Çimenoğlu stated that the steel quality of that era was highly brittle at low temperatures, whereas today’s structural steels are produced at significantly higher quality standards.
Corrosion-Related Accidents and Heavy Maintenance Costs
Prof. Dr. Çimenoğlu emphasized that the greatest weakness of structural steels is their tendency to rust (oxidize). He explained that corrosion, which grows over time, causes section loss and reduces load-bearing capacity, while corrosion of reinforcing steel inside concrete leads to concrete spalling due to volume expansion.
Highlighting that corrosion has caused major accidents in the past, Çimenoğlu referred to the 1997 balcony collapse at the University of Virginia, the 2018 bridge collapse in Genoa, Italy, which claimed 43 lives, and the bridge damage over the Elbe River in Dresden, Germany, in 2024. He also noted that the long service life of the Eiffel Tower, built in 1889, is sustained through extensive maintenance conducted every seven years and lasting approximately 1.5 years. According to Çimenoğlu, annual bridge maintenance costs in the United States range between USD 4 billion and USD 6 billion.
Discovery History and Types of Stainless Steel
Discussing the historical development of stainless steel, Çimenoğlu stated that the material was discovered accidentally in 1913 by British engineer Harry Brearley while searching for a barrel resistant to bullet friction. He explained that this steel, containing 12.8% chromium and resistant to oxidation, was first called “Rustless” and later commercially named “Stainless Steel.”
Çimenoğlu classified stainless steel types as follows:
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Ferritic: The first discovered type, characterized by high chromium and low nickel content.
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Martensitic: A hardenable type used in knives and surgical instruments, offering high wear and corrosion resistance.
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Austenitic (300 Series): Stabilized at room temperature through nickel addition in the 1920s; currently the most widely used class with the highest corrosion resistance.
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Duplex: Developed in the 1930s, containing a mixture of 50% ferrite and 50% austenite, particularly suitable for severe corrosion environments.
Explaining the mechanism behind corrosion resistance, Çimenoğlu emphasized that at least 10.5% chromium content in steel forms an extremely thin chromium oxide layer, approximately 4–5 nanometers thick, on the surface. He stressed that this layer possesses a self-healing capability when scratched or damaged.
Life Cycle Cost (LCC) Analysis and Savings Examples
Prof. Dr. Hüseyin Çimenoğlu stated that while structural steel is priced at around USD 600 per ton, 304 and 316 grade stainless steels are traded within the USD 2,400–2,600 per ton range, making stainless steel approximately four times more expensive. However, he underlined the importance of Life Cycle Cost (LCC) analysis with concrete examples:
“Although stainless steel appears more expensive at the initial investment stage, when maintenance and repair costs are included, it becomes more economical over a 30-year period. For example, replacing Tokyo’s water distribution pipelines with stainless steel generated annual savings of USD 500 million. In Melbourne, the use of stainless steel in urban furniture resulted in savings of USD 4 million over 25 years.”
In the final part of his speech, Çimenoğlu warned that stainless steel is not flawless either and that damages such as pitting corrosion, crevice corrosion, intergranular corrosion and stress corrosion cracking (SCC) may still occur. He concluded by emphasizing that if welding is required in industrial manufacturing, low-carbon “L” grades (304L, 316L) should always be preferred in order to minimize corrosion risks.
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