Seized piston

[murdo]

My Grandson has aquired another 'treasure' that has had a seized piston and has left lots of alloy stuck to the cast liner, so I am asking you gentlemen if anybody can remember the type of acid used to eat off the alloy from the liner. I used to know this and have done a few in the past but after the doctors drilled a hole in my head last year I cannot remember  what it was. Any help much appreciated.

[cardan]

Hi Murdo,

Caustic soda (sodium hydroxide) will eat aluminium and leave iron/steel (mostly) untouched. Probably still need to be honed afterwards.

Hope your head is OK.

Leon

[murdo]

Thank you Leon, will get some today.

[john.k]

If the barrel has ally fins,keep the caustic away from them.

[murdo]

Thanks for the replies.
I went to the big green hardware store today and met one of my old motorcycle friends as I went in. We stood in the shade for a chat and asked what I was getting. I told him about the seized piston in the grandson's XT600 Tenere and was going to get some caustic soda to eat off the alloy. He told me hydrocloric acid (also known as muriatic acid) was much better and safer to use, and it rung a bell in my memory. I bought 500ml for $2.00 and home. Only used a cap full and it bubbled all the alloy off within a few minutes and washed away with water. Job done ready to hone. Who would have though that pool additive was so useful out of the pool.