IME - it would depend on the cause of the corrosion. If it was induced at the factory/vendor and NOT by the user, then yes it should be covered. If someone spilled something on it.. then yeah, with you 100%
The person did not state whether anything was spilled on it.
I'll try to find out.
PS: I do not own it.. trying to help someone out!
When you work on electronics, you will generally get a sense of what the item is supposed to look like. Yes, with some manufacturing processes, it's normal to see a bit of flux and gunk on boards that might look out of place, but if every unit you work on looks like that, then it's not an issue.
When there is unusual corrosion, it's very unlikely that it is something that happened at the factory. The odds that liquid entered the unit during production, in a very controlled environment, and then was missed at every QA check along the production line is hard to believe. When sealed for shipping, the box would likely have to be visibly damaged if enough liquid were to get through to cause issue before the end user took ownership of the product.
Once the product is unpackaged and in use, it takes relatively little liquid to cause problem. A very common issue is moving an item from a very cold environment to a warm humid environment. The result is a frost buildup on the device which then melts and turns into liquid, which then evaporates and causes corrosion. So now you have the customer saying they never spilled anything on the unit, but it is damaged due to how it was handled by the end user.
Again, this is extremely unlikely to happen during shipping as most electronics are shipped sealed in plastic as well as shipped with moisture absorbing packets in the box.
Most electronics companies will provide photos of the exact damage that causes the warranty to be voided. It's surprising how easy it is to determine what exactly was spilled inside of the unit many times. Coke is different than beer is different than whiskey which is different than water which is different than milk, which is different than baby oil. Yeah, we've seen a lot inside of the computers we've worked on here.