Well I've had the company recoat this manifold for me about 1000 miles ago with their high temp ceramic coating. I got it mostly because I hate rust and the look of a rusty mild steel exhaust flange.

Well I was just taking some pictures of my intercooler piping today when I noticed rust collecting in the collector area. Why in the hell is it rusting!!! Not only is it ceramic coated, but expletive, I thought stainless steel doesn't rust. Isn't the full race manifold stainless. I would like to know why that happened even though it's coated. Does it bug me, kinda, but I really would like a explination for why the stainless is rustin and won't rub off. So I figured you guys might have some insight.

BTW the Full-Race AC manifold is just awesome.

 

Maybe impurities in the weld stainless should not rust may corrode.

 

the manifold is stainless. most grades of stainless are not rust proof...and most grades have a greater resistance to corrosion/rust than most other steels. stainless protects itself by oxidizing/creating a film on the surface of the material. break through this film, and the stainless is susceptible to corrosion. this usually only happens in harsh enviroments though. who coated the manifold?

 

Ohh okay, cause my last full race manifold did it in the same area. Maybe the water that collects there makes it more prone to rust in that area. I don't know, I was just curious. I am going to have them recoat when I get a chance to find time to take it off. I'll have them maybe spray a thinner coat in that area, maybe they didn't coat it enough. They will do it under warranty. The place I go to is Finish Line Coatings in Oregon. They are really nice people, and they do pretty good stuff.

 

Spray? Ceramic coatings should be electrostatically applied.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by beepy &raquo;</TD></TR><TR><TD CLASS="quote">Spray? Ceramic coatings should be electrostatically applied. </TD></TR></TABLE>

Ya, the Manifold is giving an electric charge and then sprayed with the coating, right?

 

Well first of all it's way down in there, unless they dip the header in their coating, I can see how it would miss that spot. Even electrostatic application will miss it since there's metal all around it the powder will go there instead. Unless they use a special powdercoating applicator for just that type of recess, it'll lack coverage.

Also, when stainless is welded, it changes the composition of the metal in the immediate area, so yes, stainless welds can rust.

 

I mean, it will form some surface rust but I really doubt it will rust through..

Most factory exhaust manifolds are stainless but they mostly all have a film of rust on them although never rust right through.

 

of course stainless will rust. any time a mild steel tool cuts, scrapes or any time it is welded, you will get rust in thoes spots.

a treatment called pickling/passifying is needed to replenish the damaged chromium layer in thoes areas

 

the phenomenon of stainless rusting is due to "carbide precipitation" which,, if i can remember correctly is when the chromium content (what gives it rust prohibiting properties)forms covalent bonds with carbon in the heat affected zone between 800 and 1500 degrees or so. the rust will always be a little bit away from the bead.

you can avoid this by using materials with low carbon such as 304L or 316L. i believe 321 is another that will not have this issue but gets more expensive and probably tougher to work, but im inexperienced to say. the other thing you can do to minimize this may be to quench the parts so that they spend the minimum amount of time in the 800-1500 degree range. this will minimize the carbon and chromium bonding. quenching stainless should not embrittle it if memory serves me correctly. stainless is only work hardenable ? i dunno, i just remember that it doesnt brittle with rapid hot/cold cycles which is why we use it for manifolds.

 

Finish line coatings...

NIC industries in White City, Oregon. Now those people are rediculous. Ive seen and heard of coatings from finish line coming off. Their prep work isnt the greatest. But they buy their coatings from NIC.

 

HPC or Swaintech seem to be good choices for coatings. There was a thread about coatings in FI with some good info a little while ago. The uncoated stainless manifolds can be cleaned up with a scotch brite pad every so often. You wont get the nice finish back...more of a darker brown...but you will help the stainless protect itself

 

Javier do you have a degree in ME or a masters in ME? and where did you get your degree from?

 

bsme from asu...might be able to get ahold of some grant $ and back early as next semester...never thought i could get paid to go to school

 

I am going to get it recoated, it is for sure the coating from finishline. So I will probably send it to TBone to get recoated. Thanks for the information guys, and answering my question. Thanks Javier and Full-Race for the awesome AC manifold. It fits perfect with my AC setup.