Morris Minor Owners Club

On another thread we were discussing freeing frozen pistons in an old engine. I've heard over the years of using Coke for this (yes, the real thing) but have never tried it. I did a little investigation of the chemistry involved, and it actually makes some sense. However, there is nothing like experimentation! The other night I remembered finding a pair of electrician's pliers lying on the dock -- left behind who knows how long ago and frozen solid. The handles would not budge, even when place in a large vice (see the victim below):



As one of my kid's -- home from college -- had left a little Coke behind I decided to give a try. I immersed the business end of the pliers in a cup of Coke. Having entirely forgotten about it, I came along about 48 hours later and pulled the pliers out. Surprisingly (to me) with just a little effort they were working freely in seconds. Now, I've had to occasion to have the same problem with a pair of needle nose pliers, and it took several days of soaking with PB Blaster and some heat to get them to move at all, and then lots of working them open and closed to smooth things up.

Both types of pliers have a similar mechanism, wherein there's a pivot pin that's a fairly snug fit. Having this experience, if I'm ever again confronted with frozen pistons I will not hesitate to top off the cylinders with some Coke, and keep it topped off for several days. I'm suspecting that the viscosity of the Coke is skinny enough to work it's way in quickly, allowing the chemical action to dissolve the rust where penetrating oils cannot go -- at least not quickly and/or without some help.

It is the phosphoric acid in the coke that does the business! Maybe Red Bull would be faster.........

Yes you might be right there Roy -

In my Army days, I used to put the brass buckles and keepers on my belt in a cup of Coke about a week out from any big parades. It got rid of any pits and scratches and made the brass shiny as new. Being young and stupid I failed to even consider what it might have been doing to my insides.

Coke does contain Phosphoric acid and this is the active ingredient that does the cleaning and rust busting. However, if you are going to be doing a lot of de-rusting then it may make sense (much cheaper!) to buy concentrated Phosphoric acid from Ebay and dilute your own rust busting solution. Just need 1% in water, although a quick google suggests coke contains about 0.1% wt/volume. And if you look there will be some scary photos of rotting teeth from coke drinking!

Apparently much worse than fruit juice which contains the weaker citric acid.