Metallic Substrate Catalytic Converter

How Metallic Substrate Catalytic Converters Work

Metallic substrate catalytic converters use a thin metal foil formed into a honeycomb structure. The foil is usually FeCrAl alloy, corrugated and stacked to create parallel flow channels. The substrate sits inside a welded steel housing, directly in the exhaust stream.

Exhaust gas flows through the channels. Flow remains mostly linear, with pressure drop determined by channel density and foil thickness. The foil is coated with a thin washcoat that holds the catalyst. The coating is stable under repeated heating and cooling and does not block the channels.

When the substrate reaches operating temperature, chemical reactions occur on the coated walls. Carbon monoxide and hydrocarbons oxidize. Nitrogen oxides reduce. The catalyst itself is not consumed.

Metal conducts heat efficiently, so the substrate heats evenly and reaches activation temperature quickly. This improves cold-start performance. Thin foil walls reduce back pressure compared to ceramic substrates, which benefits turbocharged and high-flow exhaust systems.

The structure absorbs vibration and thermal expansion without cracking. Durability is high even under rapid temperature changes or harsh operating conditions. Performance depends on substrate geometry, coating quality, and exhaust temperature, not on a single parameter. When these are matched, metallic substrate catalytic converters provide stable emission control over long periods.