I know you guys know a lot about metals, I hope you don't mind the OT post.

My mother has a pair of small, old metal bowls, I assume they are aluminum.
Last night we put canned Salmon cat food in them. When the cats were done, I
rinsed the bowls out and put them in the dishwasher. When removed from the
dishwasher, the bowls were discolored, a dark grey or black. The
discoloration is mostly on the inside- outside is pretty much untouched. We
have used the bowls this way many times before, with no problems. I don't
understand what hapened. They are 40 years old or more, and I would like to
save them. I would really appreciate any suggestions on restoring these
bowls. Thanks!!!

Regards,
Tom

"Tom Thomas" wrote in message
...
I know you guys know a lot about metals, I hope you don't mind the OT
post.

My mother has a pair of small, old metal bowls, I assume they are
aluminum.
Last night we put canned Salmon cat food in them. When the cats were done,
I
rinsed the bowls out and put them in the dishwasher. When removed from the
dishwasher, the bowls were discolored, a dark grey or black. The
discoloration is mostly on the inside- outside is pretty much untouched.
We
have used the bowls this way many times before, with no problems. I don't
understand what hapened. They are 40 years old or more, and I would like
to
save them. I would really appreciate any suggestions on restoring these
bowls. Thanks!!!

Regards,
Tom


First question is have you put them in the dishwasher before? If not, then I
understand, I've had the same thing with spun aluminum that wasn't protected
some how (anodizing?). Dishwasher detergent is very caustic stuff.
Lane

"lane" lane_nospam@copperaccents_dot_com wrote in message
...

"Tom Thomas" wrote in message
...
I know you guys know a lot about metals, I hope you don't mind the OT
post.

My mother has a pair of small, old metal bowls, I assume they are
aluminum.
Last night we put canned Salmon cat food in them. When the cats were
done,
I
rinsed the bowls out and put them in the dishwasher. When removed from
the
dishwasher, the bowls were discolored, a dark grey or black. The
discoloration is mostly on the inside- outside is pretty much untouched.
We
have used the bowls this way many times before, with no problems. I
don't
understand what hapened. They are 40 years old or more, and I would like
to
save them. I would really appreciate any suggestions on restoring these
bowls. Thanks!!!

Regards,
Tom


First question is have you put them in the dishwasher before? If not, then
I
understand, I've had the same thing with spun aluminum that wasn't
protected
some how (anodizing?). Dishwasher detergent is very caustic stuff.
Lane


Yes, they have been in the dishwasher many times before, with no problem. My
mother says that the dishwasher detergent is the same as usual.

Thanks,

Tom

IIRC, the remedy for this is to soak the inside in a solution
containing Alum (white powder used for leavening)

Tom Thomas wrote:
I know you guys know a lot about metals, I hope you don't mind the OT post.

My mother has a pair of small, old metal bowls, I assume they are aluminum.
Last night we put canned Salmon cat food in them. When the cats were done, I
rinsed the bowls out and put them in the dishwasher. When removed from the
dishwasher, the bowls were discolored, a dark grey or black. The
discoloration is mostly on the inside- outside is pretty much untouched. We
have used the bowls this way many times before, with no problems. I don't
understand what hapened. They are 40 years old or more, and I would like to
save them. I would really appreciate any suggestions on restoring these
bowls. Thanks!!!

Regards,
Tom