Stuck Cross-Shafts

[mswyka]

Finally got around to going to Home Depot and picking up a gallon of acid.  Today we went out into the driveway, put two suspension brackets into an oversized plastic paint tray and poured in the acid.  It started bubbling out the ends of each shaft and after just a few minutes had managed to eat away almost an inch of the aluminum shaft.

[mswyka]

Turns out the reaction is quite exothermic measuring up to 176 degrees F

[JDmatt]

Tip: get primer on the bare steel asap, as it will rust quickly.  Unless of course you are going to sandblast anyway. 

[mswyka]

Tip: get primer on the bare steel asap, as it will rust quickly.  Unless of course you are going to sandblast anyway.

Matt, you are right, the steel came out incredibly clean.  Only part of the suspension arm was submerged so yes, we will need perform a second cleaning.

The verdict with one gallon of Home Depot acid is that approximately 12 inches of bar were removed.  So since I put two shafts in the tank I now need to try to drive out what remains or get another gallon of acid.

[mswyka]

Today's verdict:  what is left of the shafts will not drive.  Off to buy another gallon of acid.

[mswyka]

Today's update.  After two gallons of acid we have lost 23" of aluminum bar.  Considering that they start about 18" long this would suggest that I have to get one more gallon of  acid.  After today's soak I attempted to drive out what was left - nothing was moving.  The process is very easy, but I had not bargained for three gallons of acid.

[JDmatt]

You didn't happen to buy the "eco-friendly/green" version of the acid did you?  I did the first time and when it didn't make very much progress, I got the standard stuff instead and it did the job much faster. 

[mswyka]

You didn't happen to buy the "eco-friendly/green" version of the acid did you?  I did the first time and when it didn't make very much progress, I got the standard stuff instead and it did the job much faster.

Matt, yes, it is the "green" version.  I had seen that caveat in some prior posts but when I went out shopping I could only find the "green" version.  Maybe I should do some fishing on line before we buy our next gallon.

[mswyka]

So after searching about a bit I was able to find what was described as stronger acid.  So the shafts went back into the bath with great expectations.  Remarkably, the activity in the  acid bath appeared very tame.  Except for the fuming that started as soon as the jug of acid was open there was very little bubbling.  And, while I am please to report that we now have one more useable suspension bracket, I actually think that the results of the "green" acid were more dramatic.

[mswyka]

I am pleased to report, after 4 gallons of acid, that we now have 3 more suspension brackets available for sled projects.  I am also quite pleased with how effectively the acid removes paint from the steel.  A quick clean-up after coming out of the acid bath and the new paint looks wonderful.  It reminds me of a tour of a Ford assembly plant that I had as a teenager and finding it remarkable that they would dip the entire car body in acid prior to painting.  Even though each  gallon of "green" acid seemed to disolve about 12" of 3/4" aluminum shaft, in the future, I would attempt to drill out as much aluminum as possible before going into the acid bath.  But even with the minimal preparation that we did, it was much easier on the whole than drilling or heating or pounding.  I don't know why, but the one gallon of higher strength acid did not seem to remove as much aluminum as I had anticipated.

[gixxer6]

I’m bringing back this post from wayyyy back….  I remember reading this and thought I’d give it a try , well I’m at that point where I need to remove a stuck shaft.  It’s the longer 18” shaft in the front arm, I drilled as much as I could with a 1/2” drill bit and soaked in one gallon for 24 hours, it only removed about 6 inches of the drilled sections. 

How long did you soak it before the acid quit working? 

[mswyka]

Good morning.  Wow, not sure that I ever timed the reaction.  What I can say that it was on the order of hours and not minutes - but definately less than 24 hours.  I think that the biggest problem is that of surface area as only the end of the shaft is exposed to the acid.  If I could I would probably use something like a peristaltic pump to circulate the acid bath into the end of the suspension arm.  I also found that temperature plays a big part to how well and how quickly the aluminum was disolved.  The higher the temperature the better.  The reaction is exothermic which helps raise the heat but out of doors in the winter the heat of reaction may not be enough.

[gixxer6]

I had bought two versions of acid, one was the green kind.  This is the first one I tried and found not to work well at all.  I tried the standard acid with MUCH better results.  However it seems to be taking quite a long time, must be due to the cold temps outside.  After 24 hours in the standard acid it removed several inches of shaft and was still bubbling consistently.  I’m hoping with enough time it will remove the rest of the shaft so I don’t need to buy another gallon. 

[mswyka]

Did you measure the temperature of the acid bath at any point?

[gixxer6]

I don’t have a good way of getting the temperature. 

I left it set for another day, but it’s not enough.  My local store was out of the gallon jugs so I got 2 quarts, hopefully it’s enough to finish it off. 

What did you do to dispose of the spent acid?