Annealing copper washers

Alex(Tenerife)

Alex(Tenerife)

True Classic
To start I will state I will probably buy some new dowty style washers(if I can get them here) but if I re-use my copper washers from my fuel system I know I can anneal the copper to make it soft again so as to make a good seal.

However reading online I see 2 very different opinions. Both state heat the copper to a nice cherry red. But some claim you should quench the copper in cold water where as others say allow to cool slowly.

I was always under the understanding of allow to cool slowly but is this cool quickly an "internet truth" or have I been doing it wrong all along?
 
Heating copper anneals it. Cooling has no bearing on the process. Once you reach the correct temperature copper will be annealed. If allowed to cool in air it will develop a purple oxide layer that is the old school way to determine it was correctly annealed. If you don't want to wait for it to cool, quenching will have no ill affect on the heat treatment.
 
Alex, I understand it might be difficult to get new ones where you are. But if possible I'd say that is definitely the better way to go. Due to their softness, the sealing surfaces on copper washers tend to wear and get distorted with use. Annealing will not correct these faults and you end up with sealing issues even after annealing. They are not expensive and you can order a large selection of sizes in a 'kit' online if you can't find them locally. Just my suggestion. :)
 
Copper crush washers can be annealed by hanging the washer on a stainless steel wire then heating to dull cherry red with a propane/Mapp/AC torch then allowing the washer to slowly cool in ambient air. The dark layer that develops post annealing is scale that needs to be removed before using the copper washer. DO NOT dunk in water/oil or similar to cool. This will harden the washer instead of annealing the copper washer.

Copper crush washer kits are readily available today. These are handy/useful to have in shop for any that work with banjo fittings and such.

www.ebay.com

300Pcs Copper Flat Washers Assortment Kit, Metric Copper Sealing Washers M5-M20 | eBay

15 M20 x 26 x 1.5. 35 M5 x 9 x 1. 3.200pcs solid copper slot plug set. 30 M10 x 14 x 1. Pictures View. Due to light and screen difference, the item's color may be slightly different from the pictures.
www.ebay.com


Bernice
 
Dr.Jeff said:
Alex, I understand it might be difficult to get new ones where you are. But if possible I'd say that is definitely the better way to go. Due to their softness, the sealing surfaces on copper washers tend to wear and get distorted with use. Annealing will not correct these faults and you end up with sealing issues even after annealing. They are not expensive and you can order a large selection of sizes in a 'kit' online if you can't find them locally. Just my suggestion. :)
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100% agree, time rather than cost being the motivating factor. Washers would be reused until new are found.

It was as much a question for interest. look online and people agree on heat, but disagree on how quickly to cool after.
 
Alex(Tenerife) said:
was as much a question for interest. look online and people agree on heat, but disagree on how quickly to cool after.
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Assuming these are pure copper washers, or a similar alloy like free cutting copper, heating causes grain growth of the metal. Grain growth causes the metal to be softer. Copper does not undergo a crystal structure change with heat like hardenable steels which a quench freezes in place. I've done this many times with brass or copper parts. Heat them up until they just start to glow in a dark room and then cool them off in water. If they aren't annealed you usually didn't get them hot enough or all the way through, which shouldn't really be an issue with a washer. There may be copper alloys that do exhibit some hardening capabilities but I'm sure they're not being used for crush washers. As Jeff notes, if the sealing surfaces are deformed you may still have an issue, but if they look okay it should be fine.
 
Annealing is also a time dependant process. The material needs to spend time at sufficient temperature - especially if you want truly soft rather than just stress relived. Pure copper will not harden if quenched but some copper alloys can. As others have said, should not be an issue with these washers. But - buy new ones :)
 
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