Cast Iron pitting with high heat

[johnl]

I have noticed on cast iron surfaces that have been heated pretty well, they form craters on the surface. I have seen it on exhaust headers on cars where the timimg was wrong. I was wondering if this is a standard phenomenon and what action is occurring here to cause this?

thanks

John

 

[Gokul43201]

I think what's accelerating the corrosion to the exhaust header is the high temperatures. If you have a leak in the exhaust, you will end up trapping heat between the cylinder head and the exhaust header. This increased temperature raises diffusion rates and hence speeds up the rate of corrosion.

 

[ravenprp]

Hello John,

Thank you for bringing up this interesting topic. Cast iron pitting with high heat is indeed a common phenomenon and is caused by several factors.

Firstly, it is important to understand that cast iron is a relatively brittle material and can be prone to cracking and pitting under high temperatures. This is because cast iron has a high carbon content, which makes it more susceptible to thermal shock and stress.

When cast iron is heated to high temperatures, the surface expands and can create tension within the material. This tension can cause the formation of cracks and pits on the surface, especially if the heating is uneven or the cast iron is exposed to rapid temperature changes.

In the case of exhaust headers on cars, improper engine timing can cause the exhaust gases to heat up the headers unevenly, leading to localized areas of high heat and resulting in pitting and cracking. Similarly, if the headers are not cooled down properly after use, the sudden drop in temperature can also cause thermal shock and result in pitting.

To prevent cast iron pitting with high heat, it is important to ensure even heating and cooling of the material. This can be achieved by using proper heating techniques and allowing the cast iron to cool down gradually. Additionally, using a heat-resistant coating or seasoning the cast iron can also help to protect it from high heat and prevent pitting.

I hope this helps to answer your question. Thank you for your interest in this topic.