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2020 C8 Z51
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Discussion Starter · #1 · (Edited)
My two month old Grand Sport had rust on the muffler welds and weld Heat Affected Zone (HAZ) next to the welds. These areas don't have the thin aluminium coating that is on the 409 stainless steel mufflers. Same rust that was on my September 2013 built C7 and every other 2014+ built!

Solved the issue as I did with my 2014 when I got it with a simple product called Rust Reformer. It's NOT a paint and won't peel off. It chemically turn rust (iron oxide) a blue/black. (<$10 at Walmart)

Doesn't look as good as a painting but you also don't have to take the car apart to paint! It does nothing to the non rusted areas so it can be dabbed on the whole area-no brush strokes etc. My experience with using high temp or wood stove paint if applied with a brush is it will be too think and will peel. Spaying works better but there is no way to access the rear of the muffler unless the bumper is removed!

Vette owners who are OCD and can't stand fingerprints when the close the door (not my issue) can never bend down and look at the back of the mufflers. But when the cleaning the soot from the outside pipes in their NPP, it's obvious! :sorrow:

The choice of painting requires removing the rear bumper, masking and using a spray can. Or you can buy a cover plate that with the larger NPP pipes is hard to fit without rattling. Even then the rust is there you're just covering so you can't see it from the back! Knowing it's still there may effect your ability to sleep! :moon:

This is a PDF of what was done: http://netwelding.com/Muffler_Rust.pdf
Rusted_Muffler GS.jpg
Muffler, top pic GS after 2 months, bottom pic after rust reformer

Rusted_Muffler C7.jpg
Results on C7. Top pic, after Rust Reformer, Bottom pic before. Looked the same after 3 1/2 years when I sold it!
 

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Jerry, looks like a good product to conceal that nasty corrosive look on the mufflers and you've tested it for 3 1/2 years. That area on the C5, C6, and C7 beyond the exhaust tips has always been an eyesore. I'm glad that there are several different options tried and tested by fellow SRF members to choose from and they all accomplish the mission. The General needs to take notes from this thread for the future C8 Masterpiece.

SF
Rick
 

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2020 C8 Z51
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Discussion Starter · #3 · (Edited)
Jerry, looks like a good product to conceal that nasty corrosive look on the mufflers and you've tested it for 3 1/2 years. That area on the C5, C6, and C7 beyond the exhaust tips has always been an eyesore. I'm glad that there are several different options tried and tested by fellow SRF members to choose from and they all accomplish the mission. The General needs to take notes from this thread for the future C8 Masterpiece.

SF
Rick
Yep, you'll see in my PDF there is a better welding wire than 409 for welding 409 stainless mufflers, it's called 307. It contains 8% nickel like 304 stainless and also 6% manganese that is needed to weld 409.

The problem is the muffler mfg uses aluminized 409 sheet to make the muffles. That makes it rust free longer. However, even if the weld is made rust free the area next to the welds and all spatter that sticks to the muffler back metals away the very thin aluminum layer.

The real solution is to use 304 stainless sheet and 308L welding wire, both twice the cost. To eliminate spatter use TIG versus MIG welding. That is what the Borla mufflers on my Street Rod are made from. Although I tack welded the stainless pipes and mufflers with MIG, had a pro in town finish weld with TIG.

Since all the welds on the Vette mufflers are made with MIG robots, TIG is much slower and harder to automate. If set properly Pulsed MIG can be used with minimum spatter.

A few years ago, for about a year as I recall, the Vette used titanium mufflers! They no doubt cost 4+ times as much as 304 stainless.
 
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