What is the composition inside a three-way catalytic converter?
3 Answers
The composition inside a three-way catalytic converter consists of a housing, a damping layer, a substrate, and a catalyst coating. The three-way catalytic converter is an important external purification device in the automobile exhaust system. Its function is to convert harmful gases such as carbon monoxide, hydrocarbons, and nitrogen oxides emitted from automobile exhaust into harmless carbon dioxide, water, and nitrogen through oxidation and reduction reactions. The cleaning method for the three-way catalytic converter is: 1. Use a lift to raise the vehicle and remove the three-way catalytic converter; 2. Soak and clean the three-way catalytic converter with an oxalic acid solution, then rinse it with clean water; 3. Reinstall the cleaned three-way catalytic converter and start the vehicle for a test drive.
When repairing cars, I noticed the catalytic converter mainly contains a ceramic honeycomb block with densely packed tiny channels resembling a beehive. Its surface is coated with three precious metals - platinum, rhodium and palladium - which specifically react with harmful substances in exhaust gases. The outer stainless steel shell must withstand high temperatures and corrosion, while cushioning pads in the middle prevent the ceramic core from shattering due to vibration. The worst enemies are leaded gasoline or silicone volatiles that can poison and deactivate the precious metals. For China VI emission standards, they've even added a layer of gold coating to improve low-temperature performance.
Just helped a regular customer replace this part last week. The core is a ceramic substrate with a special coating, where those microscopic channels significantly increase the exhaust gas contact area. The magic lies in that catalytic coating: platinum tackles carbon monoxide and hydrocarbons, rhodium specializes in nitrogen oxides, while palladium handles multiple pollutants. These metallic coatings are extremely temperature-sensitive – they underperform when cold, reaching optimal efficiency only at high operating temperatures. If sensors detect declining conversion rates, the dashboard instantly triggers a check-engine light.
