What are the hazards of cleaning a three-way catalytic converter with oxalic acid?
4 Answers
For many three-way catalytic converters that have been cleaned with oxalic acid, the side effects such as reduced purification of emission pollutants are mainly caused by improper cleaning. Especially, the mixing ratio of the oxalic acid solution should be prepared at a ratio of 1:10 with water; otherwise, it is easy to damage the three-way catalytic converter. More relevant information is as follows: Oxalic Acid: Also known as ethanedioic acid, it is widely used as an industrial bleaching agent or reducing agent. Due to its relatively weak corrosive acidic properties, it can greatly avoid damage to the three-way catalytic converter when cleaning substances like carbon deposits attached to it. Therefore, whether it's a 4S shop or a repair shop, they will use an oxalic acid solution to clean severely clogged three-way catalytic converters.
Let me tell you about this. Last time my car's catalytic converter got clogged, a friend suggested cleaning it with oxalic acid. At the time, it seemed like a cheap and easy solution, but it turned out to be a big mistake. While oxalic acid can dissolve the clogging impurities, its strong corrosive properties ended up damaging the precious metal coatings inside the converter, like platinum and palladium. Within a week, my car's emissions started exceeding standards and it failed the inspection. Even worse, the catalytic converter became completely ineffective, unable to properly process exhaust gases, and fuel consumption skyrocketed. The mechanic told me that residual oxalic acid would also accelerate rusting throughout the exhaust system. In the end, I had to spend a lot of money to replace the entire catalytic converter. Now I only advise people not to take such risks and instead go to a professional shop to use specialized cleaning agents—it's much safer. After all, a car is a daily tool, and safety should always come first.
From a technical perspective, using oxalic acid to clean a catalytic converter is indeed unreliable. Oxalic acid is primarily a rust remover, and applying it to the converter can damage the precious metal catalytic layer, reducing conversion efficiency. The core of the catalytic converter is a ceramic substrate coated with catalysts. After corrosion by oxalic acid, it may lead to incomplete treatment of nitrogen oxides or carbon monoxide. Once the converter is damaged, the oxygen sensor might falsely report error codes, affecting engine performance. More concerningly, residual oxalic acid can volatilize harmful gases in high-temperature exhaust, polluting the air. Don’t assume cleaning will solve all problems; professional cleaning agents like water-based solutions are gentler. It’s advisable to regularly check the converter’s condition and prevent clogging—prevention is key. Don’t let a small decision jeopardize the entire exhaust system.
From an environmental perspective, using oxalic acid to clean the catalytic converter does more harm than good. While oxalic acid can clear blockages, it damages the catalytic layer, causing the vehicle to exceed emission standards and worsen air pollution. The catalytic converter is designed to reduce carbon monoxide and nitrogen oxides; when damaged, it fails to function, releasing more greenhouse gases. Residual oxalic acid produces carbon dioxide and other harmful substances under high temperatures, which are detrimental to health. This DIY method may seem convenient but actually harms both the environment and the vehicle's lifespan. It's better to stick to regular maintenance and use certified products, protecting the planet while ensuring vehicle safety. Saving money is fine, but not at the expense of the environment for convenience.
