Muriatic Acid and Nikasil

[PB]

What is the general rule for using the acid on NiSi cylinders? Can you overdue it? I am trying to clean up a 630 cylinder and don't want to ruin it anymore. I rubbed the acid with a q-tip for about 3 minutes and then rinsed it with hot water.

 

[Jacob J.]

You can leave the acid on there for sometime, as long as there's no existing holes or pitting in the Nikasil that would allow the acid access to the softer metal underneath.

I left some cottonballs soaked with 31% acid solution in the bore of a 351 cylinder once that I thought was complete junk for two days. It had a lot of piston residue and I'd already purchased another cylinder. On a whim I decided to see if it cleaned up. I rinsed it out and did some hand sanding and it cleaned up perfectly. The acid had eaten away most of the residue and I was good to go.

 

[bullittman281]

On the one cylinder I cleaned up I found sand paper far more effective than acid. I wasn't very patient though. The NiKasil seems way harder then sand paper. I went nuts with the sand paper and it did not scratch the bore. Good luck

 

[stihl86]

On the one cylinder I cleaned up I found sand paper far more effective than acid. I wasn't very patient though. The NiKasil seems way harder then sand paper. I went nuts with the sand paper and it did not scratch the bore. Good luck

Yup, I had similar results. When done with the sand paper, I used Scotch Brite discs on a die grinder. Very good results. Except, with this saw, you can only get an o.e.m. piston, which is well over $100.00. Maybe I can melt some solder on the old piston and........

 

[PB]

You can leave the acid on there for sometime, as long as there's no existing holes or pitting in the Nikasil that would allow the acid access to the softer metal underneath.

I left some cottonballs soaked with 31% acid solution in the bore of a 351 cylinder once that I thought was complete junk for two days. It had a lot of piston residue and I'd already purchased another cylinder. On a whim I decided to see if it cleaned up. I rinsed it out and did some hand sanding and it cleaned up perfectly. The acid had eaten away most of the residue and I was good to go.

Did you notice any discoloration of the cylinder? After the acid on this cylinder it turned from a darker gray to a light gray. That is when i quit and flushed it with water. I have cleaned up a couple other cylinders before and don't remember any discoloration. Maybe it is darker from carbon?

 

[cedarshark]

I have a dozen cylinder or so, and I have tried it both ways, acid and sandpaper(600 grit) and found the acid very slow. Lots of rubbing w/ q-tips. 600 grit wet or dry with a little water is much faster. Good luck !

 

[Jacob J.]

The discoloration can be due to a number of factors- the content of silicon in the plating, the strength of the acid, other contaminants in the cylinder, etc.

The 351 cylinder I did had some discoloration from the acid which went away after hand sanding.

 

[biggenius29]

What strength is a good strength to use?

 

[PB]

Here is the cylinder after the acid. Worth trying to save?

 

[PB]

What strength is a good strength to use?

Most muriatic acid is about 31-32%.

 

[biggenius29]

Most muriatic acid is about 31-32%.

Thanks, I didnt know if you use it straight from the jug or dilute it a little bit.

 

[spudulike]

Work the acid on to the aluminium transfer, it will fizz and when it stops, rinse, rub the area with light grade wet and dry, clean the area and try adding more acid, if it fizzes, do the same again, if it doesn't then oyu have etched off all the aluminium.

Once it has all gone, lightly hone with 300 grade wet and dry, clean and you will be ready to try it.

Spud

 

[litefoot]

Here is the cylinder after the acid. Worth trying to save?

PB,
Does your fingernail catch on the scratches I see on the right side? If so, then you're probably out of luck. On a different note, I've read here that the acid will work better if you use a good detergent to remove the oils on the Nikasil first.

 

[Meadow Beaver]

Listen to Jacob the hand sanding works great.

 

[epicklein22]

Here is the cylinder after the acid. Worth trying to save?

I've had a few stihl cylinders develop the discoloration after acid bathes. Never seemed to hurt anything. I usually Q-tip the acid on till it is puddled. I let it fizz for a while (5 to 10 minutes). I then rinse it, sand the aluminum with emery cloth to rough it up and redo the cycle till it comes out good. Could take 3 cycles, but more like 5.

 

[PB]

PB,
Does your fingernail catch on the scratches I see on the right side? If so, then you're probably out of luck. On a different note, I've read here that the acid will work better if you use a good detergent to remove the oils on the Nikasil first.

That is the mark that I am worried about. I can't catch my nail on it, but I just don't like the way it looks. I can't actually see it with my eyes, the camera is letting me see more than I can on my own.

 

[dom1971]

what grit ?

 

[V3_288xp]

What is the general rule for using the acid on NiSi cylinders? Can you overdue it? I am trying to clean up a 630 cylinder and don't want to ruin it anymore. I rubbed the acid with a q-tip for about 3 minutes and then rinsed it with hot water.

Can you overdue it?
-------------------------
You did it right......but-

Heck YES you can overdue it! I did! LOL
I did a general search online and read "put some Muratic acid on it" it'll clean it right up. (my cly was Super dirty in & out) So, I got a gal of MA an 8qt S/S pot, filled it with 1/2 gal of MA (in the kitchen) dropped the Cyl in it,
turned away to wash my hands- and in about 5secs it started a slow rolling boil, it 10secs it started gassing off
and boiling so violently it was splashing out of the SS pot!
All of a sudden I realized I had "F'd up BAD" - yelled for everyone to clear the house! NOW!
Took a huge breath grabbed the pot and headed out the frt door, set it on a lil' 2ft frig sitting there
w/ 2 the new tomato plants I had just bought- ran for the water hose (all the while it was boiling like hell & gas was everywhere) I couldn't get closer than 10ft to it and dosed it with water !!!!!! til it was diluted. Crisis averted!
It was very Hot too, had to flush it too it was cool.

So... yep you can over do it trust me! LOL
I didn't get enough info, but FYI- MA and aluminum can react VERY violently together!!!

Morale of the story- NEVER do what I did!
Next day my 2 new Tomato plants were dead!

The cylinder was clean! Very clean everywhere! But it was pitted outside, the in/exh hole threads were
damaged and most of the plating was gone- So I ruined a perfectly fixable OEM cyl, because I didn't
do enough research! There was also aluminum 'slimes' in the bottom of the pan and all over the
cyl itself. Like charcoal on burned wood.
Hard lesson learned, & I was lucky, if I had panicked & left it in the house
I don't know if we could have ever gone back in it????

I am usually a perty fart smeller, but not that day!.......Whew !

 

[Canyon Angler]

Can you overdue it?
-------------------------
You did it right......but-

Heck YES you can overdue it! I did! LOL
I did a general search online and read "put some Muratic acid on it" it'll clean it right up. (my cly was Super dirty in & out) So, I got a gal of MA an 8qt S/S pot, filled it with 1/2 gal of MA (in the kitchen) dropped the Cyl in it,
turned away to wash my hands- and in about 5secs it started a slow rolling boil, it 10secs it started gassing off
and boiling so violently it was splashing out of the SS pot!
All of a sudden I realized I had "F'd up BAD" - yelled for everyone to clear the house! NOW!
Took a huge breath grabbed the pot and headed out the frt door, set it on a lil' 2ft frig sitting there
w/ 2 the new tomato plants I had just bought- ran for the water hose (all the while it was boiling like hell & gas was everywhere) I couldn't get closer than 10ft to it and dosed it with water !!!!!! til it was diluted. Crisis averted!
It was very Hot too, had to flush it too it was cool.

So... yep you can over do it trust me! LOL
I didn't get enough info, but FYI- MA and aluminum can react VERY violently together!!!

Morale of the story- NEVER do what I did!
Next day my 2 new Tomato plants were dead!

The cylinder was clean! Very clean everywhere! But it was pitted outside, the in/exh hole threads were
damaged and most of the plating was gone- So I ruined a perfectly fixable OEM cyl, because I didn't
do enough research! There was also aluminum 'slimes' in the bottom of the pan and all over the
cyl itself. Like charcoal on burned wood.
Hard lesson learned, & I was lucky, if I had panicked & left it in the house
I don't know if we could have ever gone back in it????

I am usually a perty fart smeller, but not that day!.......Whew !

Sounds like you made one biga$$, bada$$ galvanic BATTERY by using the stainless-steel pot. (Two dissimilar metals with an electrolyte between them form a galvanic cell...same thing as a wet-cell battery, like what's in your car. The stronger the electrolyte concentration, and the more dissimilar the metals are on the galvanic series, the stronger/hotter/faster the reaction, and in general, the higher the voltage created between the two dissimilar metals.)

Also, in many cases, particularly when the electrolyte is an acid, the gas that is liberated is hydrogen, and the heat that is liberated is often enough to ignite the hydrogen ... say hello to the Hindenburg.

You left it in the house? You're lucky it didn't burn your house down!

You should use a non-metallic container for "experiments" such as this.

 

[blsnelling]

On the one cylinder I cleaned up I found sand paper far more effective than acid. I wasn't very patient though. The NiKasil seems way harder then sand paper. I went nuts with the sand paper and it did not scratch the bore. Good luck

Sanding can and will go through NiSi if you work it hard enough.