# Analysis of the Material and Coating of the Nameplate of Vila D. Bosco in Macau

## TL;DR

This study analyzes the metal and coating of a nameplate from a historic building in Macau to understand its corrosion in a tropical marine climate.

## Contribution

The paper reveals the corrosion mechanism of resulfurized steel in a subtropical environment and offers conservation recommendations for similar architectural heritage.

## Key findings

- The nameplate is made of resulfurized steel with high sulfur content, contributing to internal corrosion.
- Rust consists of iron oxides like goethite, hematite, and magnetite, indicating atmospheric oxidation.
- The coatings are oil-modified alkyd resin paints with TiO2 and PbCrO4 pigments, and a polyvinyl alcohol protective layer.

## Abstract

This study focuses on the nameplate of Vila D. Bosco, a modern building in Macau from the time of Portuguese rule, and looks at the types of metal materials and surface coatings used, as well as how they corrode due to the tropical marine climate affecting the building’s metal parts. The study uses different techniques, such as X-ray fluorescence spectroscopy (XRF), scanning electron microscopy/energy dispersive spectroscopy (SEM-EDS), X-ray diffraction (XRD), attenuated total internal reflectance Fourier transform infrared spectroscopy (ATR-FTIR), and cross-sectional microscopic analysis, to carefully look at the metal, corrosion products, and coating of the nameplate. The results show that (1) the nameplate matrix is a resulfurized steel with a high sulfur content (Fe up to 97.3% and S up to 1.98%), and the sulfur element is evenly distributed inside, which is one of the internal factors that induce corrosion. (2) Rust is composed of polycrystalline iron oxides such as goethite (α-FeOOH), hematite (α-Fe2O3), and magnetite (Fe3O4) and has typical characteristics of atmospheric oxidation. (3) The white and yellow-green coatings on the nameplate are oil-modified alkyd resin paints, and the color pigments are TiO2, PbCrO4, etc. The surface layer of the letters is protected by a polyvinyl alcohol layer. The paint application process leads to differences in the thickness of the paint in different regions, which directly affects the anti-rust performance. The study reveals the deterioration mechanism of resulfurized steel components in a subtropical polluted environment and puts forward repair suggestions that consider both material compatibility and reversibility, providing a reference for the protection practice of modern and contemporary architectural metal heritage in Macau and even in similar geographical environments.