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Discussion Starter · #1 ·
Most of the bolts that I have pulled out (throttle body, valve cover gasket etc) have a green, powdery coating on them. Is this antiseize/threadlock/something else?
Apologies - if this is too basic a question to post here but my searches have been fruitless.
Thanks
 

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You mean that fugly green sh*t that's all over my throttle body is just THREADLOCKER?!?!?!? What'd they do, use a frakkin' SPRAY GUN?!?!?! grrrr....
 

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it must also be a rusty inhibitor.
 

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i HIGHLY doubt its thread locker.

my guess is that it is a rust inhibitor to prevent the galvanic reaction between a steel bolt and aluminum parts. most green bolts ive seen on VWs and Audis do contact aluminum parts.

Typically bolts that go into steel parts are just yellow passivated.
 

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How about the six bolts at the inner ends of each front axle? They connect steel to steel & they have the green stuff.

The four huge subframe bolts connect steel-to-steel &, IIRC, they have the green stuff, too.

What does "yellow passivated" mean? :confused:
 

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How about the six bolts at the inner ends of each front axle? They connect steel to steel & they have the green stuff.

The four huge subframe bolts connect steel-to-steel &, IIRC, they have the green stuff, too.

What does "yellow passivated" mean? :confused:

i didnt mean to imply that all steel to steel connections can never use green bolts.

in general passivation is a acid etching process performed on steel which removes the molecular impurities from the surface of the steel.

this cleans the bolts of scale from heat treatment and adds some corrosion resistance.
 

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I'm on the wagon for rust inhibiting. Looking at a bolt, it looks like green galvinization.

From what I understand on Loc-Tite, is green color is a surface locker like you see on indcutors on the old FM radios, so the adjuster is "locked" from moving. It is brittle so when you turn something, it's 'cracks' apart from the part.

Blue is an acutal 'thread' lock compound for semi-permenant use.

Red is also a thread lock but heavy duty. Old red Loc-Tite they would recommend you bake it onto the threads in an oven at 350-400 deg. for like 10 minutes. On SNKVNNM, I purchased a set of driveshaft bolts from Ford (for the rear end attachment) and all 4 had baked on Loc-Tite Red.
 

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Here is what the Bentley manual for my TT says about this:

WARNING! Contact corrosion!

With the extensive use of aluminum construction, corrosion caused by contact between dissimilar metals may result if the wrong fastening components (screws, bolts, nuts, washers, rivets, plugs, grommets, adhesives, etc.) are installed.

For this reason, the manufacturer only installs fastening components that have a special surface coating, recognized by its greenish color, and only uses rubber parts, plastic parts and adhesives that are electrically non-conductive.

These parts, compatible for use with aluminum, are also available as replacement parts.

Passat Bentley does not have this warning, but I suspect the TT book is referring to to the same green coating used on VW models.
 

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Discussion Starter · #17 ·
Thanks to everyone for contributing. It seems to me that the Bentley answer seems to be the most likely winner.
 

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I guess this explains the many "replace every time" bolts and other fasteners used on our cars. Not that they get overtorqued or anything, just that when they are installed they require that fresh surface coat to ensure the bolts do not react with the metal they're threaded into. And here I've been thinking VW was just trying new and different ways to get more money from me.
 
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