The different alloying elements added to
weathering steels influence the properties of
the steel in the following ways:
• Copper increases the adherence,
compactness, and elasticity of the patina.
• Phosphorous acts as a catalyst for copper
and increases the initial reactivity of the
weathering steels. It leads to evenly spread
corrosion without spots, giving the patina a
more homogeneous look. It also accelerates
the healing process if the oxide layer is
accidentally damaged
• Silicon has a positive effect on corrosion
resistance
• Chromium and nickel help to form insoluble
basic sulphates which reduce the porosity
of the oxide layer, ensuring the underlying
metal surface is protected against water
and oxygen
