Corrosion on hose necks

[wwheeler]

I am doing extensive work on the front of my engine, specifically the water pump, thermostat and housings etc. I noticed on the outside of the necks of the aluminum components, there is corrosion. On the inside of the components, there is generally no corrosion. The neck corrosion is not on the pressure side (fluid) of the clamp but rather on the air side (no pressure) of the clamp.   

I use Zerex G05 coolant but don't know what was used previously. Why is there corrosion where there is no fluid?

Is there a compound that can be used to prevent this?

[114015]

It's a common observation, Wallace.
 
Not only your car has that. You can basically find that effect on all older MB engines. Consider they are ++40 years old.

Dont' know exactly for the reason ....


Achim
(also with aluminum corrosion on his 3 engines)

[49er]

Same on mine. I just use a little WD40 on a rag to wipe it down once in a while.

John