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Arts & Communication Safeguarding Sinauli’s royal chariot discovery

investigation was conducted before any scientific treatment properties. It forms a continuous, impermeable barrier on
to assess the extent of corrosion, abnormal corrosion copper surfaces, preventing direct contact with moisture,
characteristics, mineral deposits, etc. A detailed condition oxygen, and other corrosive substances. This barrier
report for the ancient royal chariot was also generated for helps to slow down the corrosion process and protects
future reference. the underlying copper from degradation. PVA exhibits

To control reactions during chemical treatment and strong adhesion, ensuring that the protective coating
avoid complications, mechanical treatment was prioritized remains intact over time without peeling or delaminating.
for the royal chariot. Different levels of corrosion removal It is hydrophobic nature repels water, which is useful in
were employed, with minimal cleaning for less corroded preventing moisture-induced corrosion, as water is one
copper metal parts and careful cleaning for parts with
heavy calcareous deposits and encrustations. Fine tools
such as paint brushes, fiber brushes, points, needles, dental
picks, metal scalpels, surgical blades, and wooden or stick
tools were utilized.
The patina on the metal surface serves as a natural
preservative, helping to reduce further deterioration of the
metal. Therefore, it is crucial to minimize the loss of patina Figure 9. Benzotriazole acting as a chelating agent with copper atoms.
during scientific treatment. Image created using ChemDraw
Active corrosion areas on the clean and dry metal
surfaces were treated separately and with care for A B
stabilization. A 1 – 3% solution of BTA in isopropanol was
applied to these clean and dry areas of active corrosion to
prevent further deterioration. The mechanism of action
of BTA with copper metal for corrosion inhibition is as
follows:
The initial step involves the adsorption of BTA
molecules onto the copper surface. This process relies
on weak chemical interactions, including van der Waals
forces, π-π interactions, and electrostatic interactions Figure 10. After the complete restoration and preservation of the
between the BTA molecules and the copper surface. Once royal chariot. (A) Left side front view. (B) Right side rear view.
adsorbed, BTA molecules tend to form a monolayer on the Source: Archaeological Survey of India
copper surface, with their aromatic rings aligning parallel
to the metal surface. The nitrogen atoms in the BTA A B C
molecules, which have lone pairs of electrons, coordinate
with copper ions on the surface, acting as a chelating
agent and forming coordination bonds with copper atoms
(Figure 9). This coordination inhibits the dissolution of
copper ions, thereby slowing down the corrosion process.
The adsorbed BTA molecules create a protective barrier
on the copper surface, limiting the access of aggressive
species such as oxygen and water. This restriction reduces
the corrosion rate. Notably, BTA exhibits a remarkable self-
healing property as a corrosion inhibitor. If the protective
layer is damaged or removed in certain areas, the
remaining adsorbed BTA molecules can diffuse to these
sites, re-establishing the protective barrier and ensuring
continuous corrosion protection. 18,19
PVA is a widely used polymer in adhesives, coatings, Figure 11. 3D images of the royal chariot excavated from Sinauli after
and surface treatments. When applied as a protective restoration and preservation. Source: Archaeological Survey of India.
coating to copper surfaces, PVA provides several beneficial (A) Sketch image. (B) Black and white image. (C) Color Image

Volume 2 Issue 4 (2024) 8 doi: 10.36922/ac.2437