Galvanizing and brazing
Discussion
It won't work. The galvanizing process will melt the bronze brazing in the chassis and the whole thing will fall apart. Galvanizing is also very heavy and will probably weaked the rest of the metal.
If you have a chassis from a certain era there was a period of dodgy powder coating. Getting the chassis shot blasted and repowdercoated by Arch will work wonders.
If you have a chassis from a certain era there was a period of dodgy powder coating. Getting the chassis shot blasted and repowdercoated by Arch will work wonders.
It depends very much on the materials used in the galvanise and the brazing alloy.
The galvanizing would normally be zinc, the brazing alloy would probably be an alloy silver, copper, zinc and cadmium.
Obviously the galvanize and the brazing alloy has some zinc in it, but I think that the zinc in the joints may be exempt from galvanic action because it's an alloy.
It looks to me, though I'm not a metallurgist, that the zinc is sacrificial against the Iron, copper, and silver.
Edired to add;
Again depending on the brazing alloy the melting point will be between 600 and 800 degrees C. The melting point of zinc is 419 degrees C.
I guess that's what you want.
>> Edited by dilbert on Tuesday 11th October 17:38
>> Edited by dilbert on Tuesday 11th October 22:05
The galvanizing would normally be zinc, the brazing alloy would probably be an alloy silver, copper, zinc and cadmium.
Obviously the galvanize and the brazing alloy has some zinc in it, but I think that the zinc in the joints may be exempt from galvanic action because it's an alloy.
It looks to me, though I'm not a metallurgist, that the zinc is sacrificial against the Iron, copper, and silver.
Edired to add;
Again depending on the brazing alloy the melting point will be between 600 and 800 degrees C. The melting point of zinc is 419 degrees C.
I guess that's what you want.
>> Edited by dilbert on Tuesday 11th October 17:38
>> Edited by dilbert on Tuesday 11th October 22:05
Hi Steve
I'm looking to prevent what happen to Dave's car regarding the back, underneath the petrol tank.
He had to have some bit cut off and replaced.
I am not sure how bad is mine and I want to treat to have 20+ more year of happy motoring.
Thanks Dilbert (Derek?)
I will have a word with Arch, and ask them what are they though on galvanizing the chassis
Jack
I'm looking to prevent what happen to Dave's car regarding the back, underneath the petrol tank.
He had to have some bit cut off and replaced.
I am not sure how bad is mine and I want to treat to have 20+ more year of happy motoring.
Thanks Dilbert (Derek?)
I will have a word with Arch, and ask them what are they though on galvanizing the chassis
Jack
Err, not Derek, Andy.
It looks to me like you dont have to worry too much about the joints melting, but it does depend very much on the brazing alloy. The joints could become soft, and that might be an issue, depending on the weight of the assembly and the method of support.
It could be worth thinking about providing some support for the chassis if you dip it. There are also techniques that allow zinc to be sprayed, and this would avoid the thermal issues, much like the aluminium approach also mentioned.
I'd have thought that the best apporach is to identify the people who would do the job, and ask them about the problems. I'm sure they'll be very experienced in such matters, and be able to advise accordingly.
However you look at it, it's definately not a daft thing to ask for/about.
The important thing is to establish what the brazing alloy used, actually was. That gives you the temperature window, should you opt to got the hot dip route.
>> Edited by dilbert on Tuesday 11th October 22:11
It looks to me like you dont have to worry too much about the joints melting, but it does depend very much on the brazing alloy. The joints could become soft, and that might be an issue, depending on the weight of the assembly and the method of support.
It could be worth thinking about providing some support for the chassis if you dip it. There are also techniques that allow zinc to be sprayed, and this would avoid the thermal issues, much like the aluminium approach also mentioned.
I'd have thought that the best apporach is to identify the people who would do the job, and ask them about the problems. I'm sure they'll be very experienced in such matters, and be able to advise accordingly.
However you look at it, it's definately not a daft thing to ask for/about.
The important thing is to establish what the brazing alloy used, actually was. That gives you the temperature window, should you opt to got the hot dip route.
>> Edited by dilbert on Tuesday 11th October 22:11
Arch now zinc phosphate prime the chassis before powder coating it. This stops any rust from creeping under the powder coat which is what normally happens on a Caterham chassis. A chip in the powder coat alows the chassis to rust and the rust creeps along the tube until a large flake of powder coat falls off - this is difficult to spot until a large piece falls off.
Last winter I had my 7 chassis stripped and re-coated at Arch - they cut out any badly pitted rails and replaced them before the priming and re-powder coating.
Last winter I had my 7 chassis stripped and re-coated at Arch - they cut out any badly pitted rails and replaced them before the priming and re-powder coating.
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