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Is this corrosion or what? Should I lap it or not? - Nickel plated copper curse - Prolimatech Megahalems

post #1 of 29
Thread Starter 
Two times in a row, I buy a used heatsink and this is what I see:
http://imgur.com/a/bhg3y
This is Prolimatech Megahalems. Previously I had a Mugen 2 Rev. B and it had something very much like this on the base of the heatsink. It looks like the Nickel layer somehow corroded, you can easily feel those imperfections under your fingers - so that's bad. My i5-750 had deep scratches from using it with the corroded(?) Mugen and when I bought my i7-4770k, I've lapped the base of the Mugen to prevent scratching the new CPU. Now I'm switching from i7-4770k to 4790k and I bought the Megahalems and as you can see the base of the cooler is also messed up.

Now I don't know if I should lap it or install it like that and risk scratching the CPU. Prolimatech advises not to lap the base of Megahalems because it has intentional convex to compensate for the concave of CPU headspreders. I did check myself with a straight metal tool and indeed the Megahalems base is convex and the headspreader of my 4790k is concave. So if I lap the Megahalems, that theoriticaly should be no good becasue there will be poor contact in the middle (where it matters most) because Mghlms will be flat while CPU will be concave. I also obviously don't want to lap the CPU, because warranty, risk of damage, resale value, etc.

So what do you guys think, should I lap it or leave it as seen on photos? And what do you guys think this damage is, corrosion or what? The zigzag-y one kinda looks like a very deep scratch, but the dots? Unfortunately I don't have photos of the Mugen, but it looked nothing like scratches.
post #2 of 29
As long as the .. whatever it is .. are holes / dents into surface and not above surface I would just clean, apply a rice size dob of TIM in the center and install cooler as instructions say to.
post #3 of 29
Thread Starter 
Quote:
Originally Posted by doyll View Post

As long as the .. whatever it is .. are holes / dents into surface and not above surface I would just clean, apply a rice size dob of TIM in the center and install cooler as instructions say to.
The holes are... holes, but the area around the holes looks kind of elevated above the surface. It's like a crater.
post #4 of 29
lapping it wouldn't be a bad idea. i'd start with something like a 800 grit and work your way up to 2000 grit paper. you don't have to make it perfectly smooth, but just enough to get rid of the grooves that's on the surface.
post #5 of 29
Quote:
Originally Posted by Amynue View Post

The holes are... holes, but the area around the holes looks kind of elevated above the surface. It's like a crater.
Can you feel or see elevated surface on edges of holes with a straighedge?
If you cannot, try mounting it and see what the temps are like.
post #6 of 29
Thread Starter 
Quote:
Originally Posted by doyll View Post

Can you feel or see elevated surface on edges of holes with a straighedge?
If you cannot, try mounting it and see what the temps are like.
When I slide my fingernail over the messed up area it stops and I can also clearly feel the bumps with my fingertips, so it's very bad.

This is how it looks like when I rest a straight tool on the damaged area, you can see quite clearly that it's elevated:
http://i.imgur.com/QDBRAXm.jpg
post #7 of 29
I'd lap it.

EDIT: I'd sand just the protruding portions off with 800/1000 and go over the entire face with a 1500 or 2000 grit sand paper just to polish it off.
Edited by Syan48306 - 7/19/16 at 5:24am
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Hydra TH10A
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post #8 of 29
Quote:
Originally Posted by Amynue View Post

When I slide my fingernail over the messed up area it stops and I can also clearly feel the bumps with my fingertips, so it's very bad.

This is how it looks like when I rest a straight tool on the damaged area, you can see quite clearly that it's elevated:
http://i.imgur.com/QDBRAXm.jpg
I would lap / sand just the raised area, not lap the whole thing. This will remove the high spots so TIM can get a good print between CPU IHS and cooler base.

I use only a small dob of TIM in middle. A dob about the size of a grain of dry rice. This gives me a round print that just reaches the sides of CPU IHS. Here is a link to TIM application and how it works.
http://www.overclock.net/t/1491876/ways-to-better-cooling-airflow-cooler-fan-data/0_20#post_22335323
post #9 of 29
Thread Starter 
Quote:
Originally Posted by doyll View Post

I would lap / sand just the raised area, not lap the whole thing. This will remove the high spots so TIM can get a good print between CPU IHS and cooler base.
That would be the perfect solution, as it would get rid of the "scratches" while the intentional convex of the base would be preserved. While it sunds nice, I have no Idea how am I supposted to do this... Complete lapping is quite straightforward, you put a low grit sandpaper on a flat surface and slide the heatsink until the nickel is gone which would indicate that the surface is now flat, and then move to the higher grit papers to smoothen the surface. Easy. But how am I supposted to only lap a small surface of the base without scratching the area around it or ending up with concave in the place where the "corrosion" was.
Quote:
Originally Posted by doyll View Post

I use only a small dob of TIM in middle.
I will be using Gelid GC-Extreme, this tim is quite thick and I'm not sure how high is the mounting pressure of the Megahalems and if it's enough to spread the TIM nicely. Gelid includes that small paddle with the paste so I guess they suggest to use the spread method.
post #10 of 29
l
Quote:
Originally Posted by Amynue View Post

That would be the perfect solution, as it would get rid of the "scratches" while the intentional convex of the base would be preserved. While it sunds nice, I have no Idea how am I supposted to do this... Complete lapping is quite straightforward, you put a low grit sandpaper on a flat surface and slide the heatsink until the nickel is gone which would indicate that the surface is now flat, and then move to the higher grit papers to smoothen the surface. Easy. But how am I supposted to only lap a small surface of the base without scratching the area around it or ending up with concave in the place where the "corrosion" was.
I will be using Gelid GC-Extreme, this tim is quite thick and I'm not sure how high is the mounting pressure of the Megahalems and if it's enough to spread the TIM nicely. Gelid includes that small paddle with the paste so I guess they suggest to use the spread method.
Honestly, if you don't know how to do this sort of thing, you might want to consider finding someone who has experience.

Cleaning off the ridges is bacially the same as lapping, but only on the spots where the edges stick up, and only until the edges are gone. I would use very fine paper attached to something very flat and crefully move it over the ridges and looking to see it not rubbing anywhere else. Do this only enough to remove the high points. Very fine will allow you to see a change in the shiny finish .. the less change/marks it makes, the better (actually I would probably use a fine jewel's file or diamond file, but I have experience).

Warm up your tube of TIM and it will spread much easier. I often use a zip-loc bag with something heavy so it sinks the TIM blow surface of container with warm water. Gelid is really hard to use. I'd do the dob in middle.

Gelid GC is about as good as normal appliation TIM gets, but honestly the top 25-30 normal TIMs are all less than 2c difference Only thing better is Coolabratory stuff, and it's very expensive and hard to apply for only another 2.5c. To me it's not worth it.
We can gain 3-15c by paying more attention to case airflow and making sure components get air within a couple c of room.
http://www.tomshardware.co.uk/thermal-paste-heat-sink-heat-spreader,review-32799.htm
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