As I get closer to closing the case, I wanted to know how much time I
really have before the Loctite 574 cures. Is it 15, 30, or 45 minutes? Opinions seem to vary widely...
Reading the Loctite TDS, cure time varies due to many factors, including whether the metal is active or inactive. Hmm, since the case is a magnesium alloy, which is "inactive," I thought an experiment was needed...
First, using an old magnesium chain housing as a proxy for the engine case, how long can I leave the 574 sitting there before it hardens? After 1 hour, the 574 was still in a gel state and there was some "shrinkage," but it wiped right off. I did not try a longer timeframe, because I figured an hour is more than enough working time.
Next, I clamped the cover and housing together to test how well it would cure in an anaerobic environment. After an hour, I opened it up and the 574 was still in a gel state (not pictured). I reapplied the 574 and closed it back up to see how things would fare after 24 hours.
After 24 hours, I opened it up and the 574 appears to have cured. The empty spots of 574 seen in the picture were adhered to the other side.
My takeaway is that (1) 574 can sit on the case in open air for at least an hour; (2) on an inactive metal like magnesium alloy, the 574 takes longer than an hour to start curing so I don't need to be in an extreme rush bolting things back up; and (3) full cure probably takes at least 24 hours and probably longer.
I called Henkel's technical support, and they suggested that the SF 7649 activator be used on magnesium. They said that without the activator, it's possible that the 574 may take 24-72 hours to cure or may not cure at all. From my testing, it seems the 574 does cure, and so I will forgo using the activator.