Engine Case Corrosion

1972_911T · 10-24-2007, 02:21 AM

I have a 3.0 engine case that as a few patches of corrosion that has resulted in pitting of the surface in one patch it is fairly deep. What can I do about this is it a case of clean it up and hope for the best or can I treat the case with anything to prevent this getting worse? Can the pits be welded up?

Thanks Steve

304065 · 10-24-2007, 03:02 AM

Steve,

It depends really on where the corrosion is located. If it's on the flat surfaces on the outside I would hit it with some aluminum polish and call it a day. If, on the other hand, it is present on any machined mating surface or any critical area such as a bearing saddle, etc., I would post some photos and seek the advice of a professional local to you. When you say "fairly deep" are we talking a couple thousandths of an inch or a quarter inch?

The factory used Tectyl, made by Valvoline, as a corrosion preventive. There are other surface treatments available for aluminum that offer varying degrees of corrosion resistance, but they probably aren't necessary: my 41- year-old engine case is doing just fine, although to be true it had Tectyl in its early life. . . and a thick coating of oil from leaks in later life!

Ken911 · 10-24-2007, 05:15 AM

Is tectyl that crappy yellow varnish looking stuf that seems to be sprayed every where on the engine case thats so hard to clean off?

304065 · 10-24-2007, 06:20 AM

Quote:

Originally Posted by Ken911

Is tectyl that crappy yellow varnish looking stuf that seems to be sprayed every where on the engine case thats so hard to clean off?

The very same. Does a great job of protecting the magnesium engine and trans cases.

1972_911T · 10-24-2007, 06:28 AM

The corrosion is not anywhere crusial ie mating surfaces its on top of the case about an inch or 2 above the spigots. There is a little patch around a couple of the head studs but im not sure how bad this is untill I get the studs out hopefully it wont have penetrated too much. The patch above the spiggots is about .5mm to .75mm deep the case below it seem quite thick at that point so I dont think as it is it will be an issue if I can stop its spread.

Ill post some pics later

Steve

1972_911T · 10-25-2007, 02:06 PM

Heres some pics of the corrosion I cleaned it up a bit with the wire brush today, im not sure if its njust best to polish it and leave it or if it needs further attention?

I think this case would be a good candidate for the abrasive tumble cleaning shown in the case cleaning theread, it really is in need of a good clean up.

Steve

304065 · 10-25-2007, 02:23 PM

I would polish it with a nonmetallic abrasive like a scotch-brite Roloc disc, try not to take off too much metal, and make it as smooth as possible. The case will be thinner but the goal is to eliminate the stress risers.

If you use a steel wire brush it will embed particles of steel in the aluminum which will make the corrosion worse.

If you want to protect the aluminum, use Henkel Alumiprep and then Alodine. These should be available globaly. Perhaps this step is overkill, however. These chemicals are probably dangerous so use appropriate gear and precautions.

jluetjen · jluetjen's Garage

Quote:

Originally Posted by Ken911

Is tectyl that crappy yellow varnish looking stuf that seems to be sprayed every where on the engine case thats so hard to clean off?

BTW, Tectyl comes off easily with brake cleaner, of if you want something that's a bit friendlier to work with -- mineral spirits. I use mineral spirits for most clean-ups and leave brake cleaner for the small jobs or where I need it to quickly evaporate clean.