Quick statement if you wanted to go another step further before installation of your turbo kit or maybe fancy exhaust just something to keep in mind on parts made of Stainless Steel.....I suggest taking some sort of wire wheel or rigorous brushing to the welds otherwise they will start rusting/corroding quicker than if they were cleaned up.

That grey or color from the weld are just impurities and trash and basically oxidation from the joint and welding process which has risen to the surface. Or if some carbon steel something scratches the SS it will cause rust as shown below with blue arrows.

Another quick note is that just because someone says its stainless doesn't mean it won't rust or isn't magnetic...just my two cents on welding and metallurgy.

I think most of the turbo system or exhaust manufacturers are doing this, but if they don't I'd suggest doing it especially if you are putting it in a DD or not coating the parts.


Here is an example

 

409ss will show scale no matter what since it has higher carbon content

If the stainless weld is a gray color its from to much heat during weld process

 

I disagree on 409 always having scale no matter what. I've welded plenty of 409 and 410 with 309 or 308 and resulted with great color and didn't see any "scale"

I would agree that color is also a great indicator of heat input and if it's grey it's too hot or progression is too slow. It can be very difficult to not make a GMAW(MIG) weld to not look grey.

 

409 scales look at any factory exhaust
Look at any magnaflow ss exhaust
Look at any ss flowmaster exhaust

All are 409 all show scale over time


Im not referring to weld joint im referring to over time

 

Ahhh I gotcha.