Hello,
I've been asked to make cast repairs more often these days. I have no problems making the repairs and have done many over the years but these days they are bringing me some pretty worn out things to weld. They tell me the economy is to blame and the clients want repairs rather than replacement.
In my opinion, the large pump they brought me today was corroded to the point that the metal wasn't even metal anymore. I could lightly tap it with a chipping hammer and it broke away in 1/4" chunks. I tried grinding it and it didn't even make sparks. It looks like it has a 1/16" metal skin around the outside edge and the remanding 3/16" is corroded from the inside out. I can't find base metal to even start a welding repair with. My question is what do they call this type of corrosion? Is it oxidation? Contamination? The pump was for a massive chlorine water treatment pump and was 25 years old. I said it was not possible to weld and was looked upon by the bean counters as an incompetent. I showed them that I could lightly chip the base material away and it was no longer metal but they were not convinced. Any help on what type of corrosion this is called would be appreciated. The replacement pump would cost around $10K and I can't even light an arc on the old one as the metal just rolls off. Thanks for the help.
I would go with oxidation, as chlorine is an oxidizer.
When it's that bad think the most accurate term would be "exfoliated"
Exfoliation is the result of long term intergranular corrosion.
If your audience isn't into technical terms than "totally rusted out" is just as accurate.
Lawrence,
I take the liberty of not agreeing with you. Exfoliation is the result of poor rolling, usually at a lower temperature than necessary.
Giovanni S. Crisi
Sao Paulo - Brazil
I think Lawrence is referring to Exfoliation Corrosion, where corrosion products build up in between the grain boundaries and separate them, and you're referring to the exfoliation fracture of cold drawn steel products, such as wire? So I believe you are both right.
I agree.
Giovanni S.Crisi
I would hand the bean counters the torch and have them try and weld it...
Thanks all. I would love to tell them to weld it themselves. It's funny when some college kid tells me "why don't you just braze it"?
I answer that it has to actually be metal in order to braze it and ask them if they've ever seen metal that you can pull apart with your finger nail.
Blank stares.....................
When they ask you why you can't weld it with Titanium or something, be sure to tell them that the only rod that will weld it is "Unobtanium", and it cost $10000.00. If they say that is OK, add "Per inch".
Joe Kane
Joe,
Where might one find "Unobtanium" in ASME section II? :-)
Regards,
Gerald
Gerald
You can't get any Unobtanium any more. The Ferromanuerium Corporation got an injunction from a crooked federal judge years ago.!.! The inventor of Unobtanium, Mr. James Danaher, lost his life savings in his unobtanium corporation.. A truly sad story.
Joe Kane
Joe,
A sad story indeed. I guess we will have to contact Ferromanuerium corp for a replacement rod. I wonder if they have bovinianexcretium rods? I hear they are even more expensive than the Unobtanium rods.
Regards,
Gerald
good one Larry!
Ptbased,
A pump for chlorinated water that has been 25 years in service deserves a honorable retirement, complete with a ceremony with speeches, handing of a sheepskin and a music playing band. Ha ha ha. She's given more than was expected.
Giovanni S. Crisi
Sao Paulo - Brazil
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