Finding materials to help the bronze monument is not rusty

Dr. Pham Dang Dich, working at Research Center for Casting and Metallurgy Technology Development (Hanoi Association of Science and Technology Associations) has completed the project " Research on technology for manufacturing copper alloys with fasting strength. Highly worn for construction and restoration of monuments located in Hanoi ", to select the copper alloy system suitable to the Vietnamese climate.

This is the first research project of materials technology in the field of bronze monuments in the country.

Most are green rust

Hanoi people probably remember the phenomenon of monumental Ly Thai To after a few meals " rain beams, sunshine " was smeared with green rust. The city has covered it up and repaired it. Now, the monument to Ly Thai To is no longer "rustling" green.

Dr. Pham Dang Dich, Chairman of the project confirmed, four monuments built by us in Hanoi (Memorial Monument of Bac Son, monument of Ly Thai To, monument of Vietnamese workers, winter Hanoi reliefs) 1946) all have local blue rust at different levels. Only the Lenin Monument is not affected.

In addition, through monumental surveys in neighboring provinces such as General Le Chan, Cultural celebrity Nguyen Binh Khiem (Hai Phong); Quoc cong Tiet bao Hung Dao Vuong Tran Quoc Tuan (Nam Dinh); Dien Bien Phu victory (Dien Bien); The late General Secretary Nguyen Van Cu (Bac Ninh), the status of these monuments is the same as in Hanoi.

The main cause of this situation is because the monument's casting material is copper alloy, but most of the alloy is re-cooked from collected materials, does not control tin components, so there is no good corrosion. Meanwhile, the air environment in Vietnam shows signs of increasing pollution (concentration of SO ₂ , NO ₂ . in high air) plus the tropical climate, which always has high humidity, stimulating the Corrosion to the surface.

Monument of Vietnamese Workers, Hanoi (Photo: Vnexpress)

In addition, connecting parts of the monument to each other as well as of the monument to the inner bracket may not meet the technical requirements.

Mr. Dich affirmed that, if it is not possible to select a system and label with high corrosion resistance, it is impossible to have beautiful and durable bronze monuments.

Good material was found

After a thorough research, Dr. Dich has selected the copper alloy of the plural system (CuSnZnPb1A) with high corrosion resistance, meeting the standard for casting bronze statues. The scientific analysis and testing methods together with the inspection of the statues in the outdoors have shown that this alloy copper has good casting properties and the mechanical properties are perfectly suitable for manipulation. Bronze monument in Hanoi.

Not only that, this topic also identified the process of alloying in medium frequency furnaces on an industrial scale. Research results show that, smelting technology is relatively stable, creating copper alloy marks to ensure composition, corrosion resistance by mass loss method and high electrochemical corrosion, good dilution, mechanical and physical properties approximate the requirements. This is one of the important conditions for casting bronze monuments of all kinds, including large scale.

Dr. Dich has tried six monuments (three statues of Quan Am, two " Girl pouring water " statues, a " Water girl " statue with copper alloy marks and smelting technology that have been studied and selected. That is, three of the six statues have been tested outdoors in the space of the family's air-conditioned courtyard in a residential area with air conditions characterized by invasive gas components. Harmful objects such as SO ₂ , NO ₂ . and high humidity.

As a result, after 180 days in the same air environment in the north, there was no local green rust on the statues. The color of the statues becoming darker, especially the polished " Water Girl " model after casting, becomes dark brown.

According to the sculptor Ta Quang Boi, the bronze statue to be outdoors in color changes over time as black as beautiful.

Dr. Thai Ba Minh, Chairman of the Board of Appraisal and Evaluation of the project has successfully completed the research contents and objectives. The Acceptance Council has proposed the Department of Science and Technology and Hanoi People's Committee to create conditions for the topic to be applied with other monuments, art and civil works.

According to the Council of Acceptance, the technology of manufacturing copper alloy marks will serve practically for the construction of outdoor bronze monuments in the preparation period to celebrate the 1,000 years of Thang Long-Hanoi.