What Causes White Oxidation Spots on Engine Blocks?

[DeFernando]

Engine block white oxidation spots are caused by: the engine being an aluminum alloy engine or the engine coming into contact with coolant, battery acid, or water. Precautions for engine maintenance are as follows: 1. Fuel must be clean: High impurity content in fuel can accelerate the wear of the electric fuel pump, reducing its service life. Unclean fuel can also lead to clogging of the fuel filter and fuel injectors, affecting fuel supply pressure and normal fuel injection volume, thereby diminishing engine performance. 2. Correct fuel selection: Engines have high requirements for fuel quality and grade, with fuel-injected engines having even higher demands. For vehicles equipped with catalytic converters and oxygen sensors, only unleaded high-octane gasoline should be used. If leaded gasoline is used, the exhaust catalytic converter will fail after driving more than 400 kilometers, the oxygen sensor will malfunction, and the normal operation of the engine will be affected.

[Finn]

I encountered a similar issue last time. The white spots on the engine block are mainly caused by coolant. When antifreeze leaks onto the block surface, especially on aluminum blocks, the ethylene glycol inside decomposes under high temperatures to form acidic substances, which corrode the metal surface over time, resulting in white frost. Additionally, residual alkaline car wash detergent left uncleaned during engine washing, or long-term driving in humid coastal areas where salt and moisture interact, can also cause this. I recommend having the mechanic check the water channels and joint seals during every maintenance session. After all, this type of corrosion can spread gradually, and if it leads to block cracking, it becomes a major problem. If addressed promptly, simply sanding the area and applying some anti-corrosion coating can resolve it.

[LeAyla]

In our repair shop, the most common issue is this white powdery substance appearing on aluminum engine blocks. Essentially, it's electrochemical corrosion – a micro-battery reaction occurring on the metal surface. For example, when you change the coolant without properly bleeding the air, bubbles form in the system causing localized overheating; or when using substandard antifreeze, the pH balance is disrupted; some owners even prefer rinsing a hot engine directly with water, where drastic temperature differences allow moisture to seep in. Last week, we handled a vehicle that suffered from frequent short-distance driving, where the engine never fully warmed up, leading to long-term condensation buildup in the engine block crevices. To completely resolve this, it's necessary to thoroughly clean the corroded areas, replace with qualified antifreeze, and remember to let the engine warm up sufficiently during daily use.

[SanMadelyn]

This type of white oxidation spots is particularly common on aluminum alloy engine blocks. The principle is that the metal reacts with corrosive agents to form aluminum hydroxide. The most typical case I've encountered: a car owner used the vehicle in a coastal city for three years, and the engine compartment was covered with white powder. Subsequent testing revealed that chloride ions in the sea breeze accelerated oxidation, combined with residual alkaline foam from car washing, both contributing to corrosion. Additionally, if there are air pockets in the engine block casting, it's easier for moisture to accumulate and form corrosion points. The key to prevention lies in keeping the engine compartment dry, using neutral cleaning agents, and during rainy seasons, it's best to use compressed air monthly to blow out accumulated water in corners.