Watch Those Cure Times!


(Kirbert - author of the Book, former owner of an '83 XJ-S H.E.) #1

Doing Hurricane Michael cleanup here and found I needed to do some repair work on my aging McCulloch chainsaw – and that required the use of a flange sealant. It just so happened that I have a half-full tube of Loctite 573 left over from my Jaguar-owning days, and it actually appeared to still be good.

First attempt failed, though – the saw was incontinent, leaking bar oil. That, in turn, led me to do some internet research to see if Loctite 573 goes bad on the shelf. Didn’t find any age warnings, but I did learn that 573 is Loctite’s slow-cure product, intended for applications that may take a while to fully assemble. A chainsaw is decidedly not that, it can be torn to bits and fully reassembled in an hour or two. Loctite 573 also, oddly enough, takes longer to cure when used between aluminum flanges than steel, requiring only 24 hours in steel applications but 72 hours when used on aluminum. It didn’t really say any of that on the tube, but it makes sense that such a sealant requires some time to cure.

It also turns out that it takes longer to cure if the parts don’t fit together as well as you might hope. The cure time is a function of the joint gap, with tight-fitting joints curing more quickly than joints that end up with a few thou of gap. Fortunately, the flanges on the bar oil tank on the chainsaw fit very tightly indeed.

So I let it sit for 72 hours the second attempt, and now it doesn’t leak.

I think Loctite 518 is a fast-curing product, but even so, it probably wouldn’t be wise to just slap the engine together and try to start it immediately, especially if you’re a mech that works fast.


(Mark Eaton) #2

Interesting.

It makes me think of times when I have slapped 518 on, and started up immediately, versus assembled and come back to the job next weekend. I “think” (and maybe I am imagining it) that I have had better results not stressing the joint immediately. Which would make sense.

Doing a quick internet search I see 518 is rated at a 4hr cure time. I am sure I have assembled cam covers on various engines and started them up right away, not thinking to wait to let it cure.


(Mark Eaton) #3

For completeness here is an image from the datasheet

Looks like you need 24 hrs to be safe …


(Con Saris) #4

So are you saying we should read the instructions?:rofl:
Con


(Kirbert - author of the Book, former owner of an '83 XJ-S H.E.) #5

I’ve never SEEN those instructions! The instructions on the tube basically say to apply a bead and assemble.

The fact that a larger gap requires a longer cure time perhaps explains why the stuff doesn’t dry up in the tube. It’s called anaerobic which means it cures in the absence of air, so why doesn’t it cure in the tube? I guess it’s just a really big gap.

But what’s up with the cure time and strength difference between aluminum and steel? How does the stuff even KNOW whether it’s been applied to aluminum or steel? Does Loctite have a different product for use on aluminum?


(Mark Eaton) #6

46a0d3f3d79007680fd5b840501e69d7


(Con Saris) #7

all I can say is :+1:
Con


(Steve) #8

The Loctite product you mentioned in the 1st post is to be used on a variety of metals, verbatim from the data sheet: “Aluminum, Brass, Bronze, Copper, Steel, Stainless Steel, Cast Iron, Titanium”

How does it know how fast to cure on Al vs Fe – one may speculate that the curing is catalized/initiated by the presence of small amounts of metal ions, as most of the anaerobic products’ descriptions I saw specify metal substrate.

It is a far-fetched explanation, I admit it, but given that the maximum gap size of these products (0.01-0.05"), some type of chemical interaction with the sealing surface seems reasonable.


(chris gruchawka 1988 XJ-SC) #9

Wow I’ll start think about alternatives in cooking😊