C-type steel, also known as low alloy steel, has a carbon content of less than 0.2 weight points per point. Copper, chromium, nickel, phosphorus, silicon, and manganese are mainly added as alloying elements, with a total amount of no more than 3-5 wt points. The chemical composition of these steel alloys can quickly form a rust proof/iron oxide layer through special formulas, providing a weather resistant coating for the base steel
The corrosion rate of C-shaped steel is very low, and bridges built with C-shaped steel can easily reach the planned lifespan of 120 years, but the maintenance cost is very low. In fact, C-shaped steel structures also provide many other advantages, including reducing the total life cycle cost and improving safety. Due to the lack of maintenance oil paint system and shortening the inspection cycle,
The demand for paint also means that volatile organic compounds will not be released into the atmosphere, and construction speed will accelerate. From the perspective of initial material cost and maintenance, the cost of C-shaped steel bridges is generally 5 points lower than traditional painted steel alternatives. It was launched on the market in 1933 to eliminate the need for truck painting and other maintenance. This alloy has a rusty or rusty appearance. Nowadays, it is particularly favored by some builders, And decorated with many Zuming construction and prehistoric sites, such as the John Deere International Headquarters in Illinois and the Northern Angel Monument in the UK. The copper rust of C-shaped steel not only has higher corrosion resistance than low-carbon steel, but also has an attractive appearance and self-healing ability.
The excellent corrosion performance of C-shaped steel is nominally based on the addition of copper and nickel content in the alloy, although other alloying elements such as chromium, manganese, and phosphorus also contribute. Copper is particularly important for maintaining the bonding between the oxide layer and the metal and mitigating corrosion
Steel is allowed to rust, and due to its alloy composition, the rate of rust is slower than traditional steel. Rust forms a maintenance coating that slows down future corrosion rates. Research has shown that repeated dry/wet cycles are very important for forming a fine adhesion rust prevention layer. Rainwater can effectively wash away the surface of steel and is easy to drain, A recent study on highway bridges constructed with S355J 2W steel in the Czech Republic has shown that these structures do not have gaps for collecting water, as corrosion can occur in these areas and do not form a maintenance bronze color.
c型鋼的氧化過程能夠繼續幾年,然后外表由緊密結合的涂層安穩.這在很大程度上取決于當前的大氣條件.磷和硫在銅綠層構成中的作用也很重要,由于低溶解度的硫酸鹽或磷酸鹽是在堿性鋼和已有腐蝕物之間構成的,前提是外表暴露于周期性枯燥的濕循環ISO 9223指出"用SO 2污染大氣會構成更具維護性的防銹層.Leygraf和Graedel支撐這一觀點,但他們也以為,大量非金屬氧化物會導致水層激烈酸化,從而阻止銅綠假單胞菌的構成.磷還被證明在鋼外表構成維護性鈍化膜,能夠防止侵蝕性離子和水分的進入,從而支撐構成連接和細密的銅綠層.然而,磷會對合金的晶粒結構和鋼的機械強度產生不利影響,因此添加低含量的硼或碳來康復所需的晶界.
The oxidation process of C-shaped steel can continue for several years, and then the surface is stabilized by a tightly bonded coating. This largely depends on the current atmospheric conditions. The role of phosphorus and sulfur in the formation of the copper green layer is also important, as low solubility sulfates or phosphates are formed between alkaline steel and existing corrosives, The premise is that the appearance is exposed to periodic dry wet cycles, as stated in ISO 9223  Polluting the atmosphere with SO2 will form a more maintainable rust prevention layer. Leygraf and Graedel support this viewpoint, but they also believe that a large amount of non-metallic oxides can cause severe acidification of the water layer, thereby preventing the formation of Pseudomonas aeruginosa. Phosphorus has also been proven to form a maintenance passivation film on the surface of steel, which can prevent the entry of corrosive ions and water, thereby supporting the formation of a connected and fine copper green layer. However, phosphorus can affect the grain structure of alloys and the mechanical properties of steel The mechanical strength has an adverse effect, so low levels of boron or carbon are added to restore the required grain boundaries