2 piece EM welding, skimming, and coating

[Stetina]

Gerald,

Thankyou for your reply,  I am attemting to have the welding done.  The guy
I've found claims "if its weldable, I can do it...I can weld 2 razor blades
together if needed... " The other thing I noticed is that the EM exhaust
flanges are not completely in line when checked against a flat surface.
They have deffinately moved... I'm hoping that this can be remedied by
skimming that side .020 or something (like one does when you mill a head).
I just hope that the pieces can be held to allow this.

On your ceramic coating idea, I have serveral items coated with the jet hot
stuff.  It appears to hold up well on the motocycles and even the 323i
header which is still wrapped (supposedly not a good idea but it was so
dificult to do I haven't yet removed it!),  but the 2 piece EM I have is /
was coated and in many spots it has come off big time..both in chuncks and
solidified "drippings".   I don't believe it will work on something as
extreme as a turbo manifold.  The heat barrier they all tout I think is a
doubtful claim also...maybe on a "space shuttle application", but that type
of thing is obviously a totally different 'cost is no object' animal. The
heat from a turbo system is much more intense then a regular exhaust system,
especially if your running high boost. If it rusts so what ?  It'll take
175+ years for that casting to rust thru!     I'd save your money on that !

Joel   87 5000TQ, 90 200TQ wreck, 91 200TQA20v, 79 323i
----- Original Message -----
From: Gerard <gerard at poboxes.com>
To: Stetina <stetina at easy-pages.com>
Sent: Thursday, August 17, 2000 1:40 PM
Subject: Re: 2 piece EM welding ?


> I think it's a pretty regular casting. I traded my automatic gearbox
> for a 2-piece to replace the badly cracked 1-piece that came off
> my '89 200. A few months ago I had the front section welded up as
> it was cracked in the same location as you describe. The "Y" were
> it empties into the turbo turbine housing was cracked as well and
> there was a small crack near the connection between the 2 halves.
> The weld seems pretty good, but now the entire thing is rusted as
> the welding company covered the thing in a thick red coating. That
> after I paid for sandblasting in prep for a ceramic coating. They
> had to clean it off with an acid (similar to the spirits of salt
> I used on some other metal bits) and it just does something to
> make the surface corrode.
>
> I think that a new front section wouldn't last that much longer
> compared to a decent solid welded unit.
>
> As mentioned above, I have decided to send this in for a metal-
> ceramic coating both internally and externally. I could not get
> the "real deal" zirconia coating done as it is a bit complicated.
> Yttria-stabilised zirconia ceramic coatings are used in jet engines
> to project the aluminium turbines from the heat. That would prevent
> my manifold cracking again. I have to settle for a ceramic that is
> simply sprayed on and baked, but it does do the job of reducing the
> amount of heat transferred to the metal of the exhaust. I'm not
> doing it for performance, just for longevity.
>
> That's my story on my rare 2-piece item. :) At $1000 for a local
> replacement, I don't think I'm doing to bad paying the $150 for
> welding and ceramic coating. :)
>
> By the way, there are obviously many opinions on the ceramic thing.
> I know the proper thing (full proper process) does the trick. It
> must if used in jet engines to let aluminium withstand near twice
> it's melting point in heat. The stuff normally applied by those
> performance shops is a cheaper process, but not useless at all.
> It is quite good as a heat barrier and a corrosion preventer. :)
>
> G.
> --
> gerard at poboxes.com
> q-list info: 1989/90 200 (mac13a MC-1)