Rusted exhaust

[NV245]

I know that Ram truck manual regeneration calls for parking on gravel or concrete, not asphalt. I might suggest Utube videos of manual regeneration such as this one. http://youtu.be/c1aK-WACWsY


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[doc73]

I would think you guys drive enough miles that the engine will not need to regen per say, it will do it while you are on the road. With my chevy it will not need a regen if I travel mostly highways.... SO they say.

[NV245]

Regen is to clear the particulate emissions collected in the Diesel particulate filter(DPF). The particulates (soot) are usually created during acceleration (remember the black smoke that used to be seen from semi-tractor stacks). Regeneration is usually done at speed, the proper conditions must be met before the cycle begins, and there is usually no indication that it is happening. However, if the DPF fills and conditions for automatic regeneration are not met, you will get a warning of some kind, and a manual regen is the quickest way to get back to normal operation. So, while it has not been noticed, your Silverado has probably done several regenerations without your knowledge.


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[doc73]

Oh, I am sure it has done its thing in the last 15,000 miles. My point was, if the regen is happening along the highway at speed that will hopefully keep the temps down enough to not melt the heck out of your rig. Especially if the heat wrap, that seems to be the failure here, is removed. But, of course, I do not know if I'd want to run that risk with my 400k motorhome. It seems sad that instead of taking the responsibility and correcting an obvious issue everyone points fingers at the "other" guy.

[NV245]

Speedmerchant posted in a previous thread about not using an insulating wrap on his tailpipe and now has 12,000 miles without incident. I haven't seen a pickup that uses Diesel particulate filter use insulating wrap on the tailpipe, however, I feel that the material chosen for the tailpipe is more the rust problem than the insulating wrap. The replacement pipe from manufacturer was priced at $80, that does not sound like stainless exhaust pricing. Yet, some designer of the coach had the tailpipe insulated, should a heat issue occur, it would be interesting what the results of a lawsuit would be.


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[doc73]

Yeah, I would think it would be fine at this point. I guess it was someones bright idea to put it there. If Freightliner put it there I would say it was because they really have "no idea" how their chassis would be used or configured. But sounds like from a previous poster it is a FR addition. At least it is a relatively cheap fix.. Minus the grief causing heat wrap.

[Campin Cajun]

Rust is caused by oxygen and moisture, it has nothing to do with heat. It forms fast if the moisture is brine (salt).

So if you drive in the rain or travel to humid areas the rust (oxide) will develop sooner.

My advice is to remove the wrap, treat the pipe with a rust preventative then reinstall the wrap.

[doc73]

Originally Posted by Campin Cajun

Rust is caused by oxygen and moisture, it has nothing to do with heat. It forms fast if the moisture is brine (salt).

So if you drive in the rain or travel to humid areas the rust (oxide) will develop sooner.

My advice is to remove the wrap, treat the pipe with a rust preventative then reinstall the wrap.

Yeah, I guess they did put the wrap there for a reason. Being only $80 for the replacement steel part, my guess is it is very pricey or at least unavailable in a SS version to avoid the rust again?

[klucas]

Here is the final result. Stock pipe when I took it off. Completely rusted under the heat sock. New elbow and tip I installed.


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[po 185]

nice job

[dan-nickie]

I like it. Gives you more clearance for your mud flap to doesn't?

[Campin Cajun]

Nice job, was the inside of the rusted pipe also rusted?

[klucas]

Yes. The inside was rusted and flaking apart. It was completely detached from the dpf filter. The elbow does give the mud flap much more room and it doesn't hit like the original pipe did. It also gives me clearance to change the serpentine belt much easier. I did that this weekend as well. My thought are the reason they have the heat sock is for a parked regen. I do a lot of highway driving and never had a parked regen so I am not to worried about loosing that heat sock. I will however keep and eye on it and if I see any heat damage start I'll cover it with header wrap. From what other have said it hasn't been an issue. I also think the temps are a little lower with the def fluid compared to the original diesel regen process.


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[silver]

When I replaced mine I added a second strap back by the dpf filter. When the original pipe rotted I almost lost it and that custom flat tip. This way I figured I would keep it next time.

[rockfordroo]

Originally Posted by Campin Cajun

Rust is caused by oxygen and moisture, it has nothing to do with heat. It forms fast if the moisture is brine (salt).

Not true. Increasing temperatures increase almost every chemical reaction. Rust (corrosion) is simply a chemical reaction.

In the power plant I work at, we try to reduce temps as much as possible to reduce corrosion, for example, in steam generators. Also try to keep Oxygen levels low.

[wmtire]

Originally Posted by rockfordroo

Not true. Increasing temperatures increase almost every chemical reaction. Rust (corrosion) is simply a chemical reaction.

In the power plant I work at, we try to reduce temps as much as possible to reduce corrosion, for example, in steam generators. Also try to keep Oxygen levels low.

I think we may just have a difference of terminology being used. My unscientific understanding is that rust is actually caused by the reaction of iron, oxygen, and water........ but is accelerated by other things, like temperatures, as per this link below:

https://www.couplertec.com.au/index....&Itemid=200003

I think Campin Cajun and Rockfordroo are both offering good advice to help out.

[rockfordroo]

Originally Posted by wmtire

I think we may just have a difference of terminology being used. My unscientific understanding is that rust is actually caused by the reaction of iron, oxygen, and water........ but is accelerated by other things, like temperatures, as per this link below:

https://www.couplertec.com.au/index....&Itemid=200003

I think Campin Cajun and Rockfordroo are both offering good advice to help out.

Not sure I agree with the word "terminology," but maybe with "range." When you speak of a "normal temperature range" i.e., those most of us deal with (say 0F to 100F, then temperature doesn't make too big a difference and Campin Cajun is in the ball park. In other words, the rust on your frame isn't too much influenced by the normal range of temperatures that your frame sees (0F-100F). But when you start to talk about elevated temperatures, like those we're talking about on this exhaust pipe (~1400F if I'm reading this thread correctly) then temperature can really drive a chemical reaction.

[wmtire]

Originally Posted by rockfordroo

Not sure I agree with the word "terminology," but maybe with "range." When you speak of a "normal temperature range" i.e., those most of us deal with (say 0F to 100F, then temperature doesn't make too big a difference and Campin Cajun is in the ball park. But when you talk about elevated temperatures, like those we're talking about on this exhaust pipe (~1400F if I'm reading this thread correctly) then temperature can really drive a chemical reaction.

I agree, but the chemical reaction(causation) is one part, and the temp is another. Don't you have to have the initial chemical reaction begin (rust), before the temp can drive it? Am I missing something?

[rockfordroo]

Originally Posted by wmtire

I agree, but the chemical reaction(causation) is one part, and the temp is another. Don't you have to have the initial chemical reaction begin (rust), before the temp can drive it? Am I missing something?

You're talking about an uncoated exhaust pipe. There's always moisture in the air; the reaction is always occurring. It's just a matter of how much. Dry it out, it slows down, get it wet, it speeds up. Cool it, it slows down; heat it to 1400F, it speeds up. Protect it with paint, it slows down. Scratch off the paint, it speeds up.

We can't stop corrosion. We can slow it way down in some cases so for all intents and purposes, it's not occurring, but it is still happening. Even with sacrificial anodes, where the anode is supposed to corrode, there is SOME amount of corrosion of the protected material. It's just very, very, very slow.

The only thing I can think of that MIGHT stop ALL corrosion is if you have a cathodic protection system, where you put a voltage on the material in such a way that it drives the chemical reaction "the other way." Power plants do this on their underground piping. I'm not an expert on cathodic protection, but I've seen pipes protected by it; from the looks of the pipes, I'd say it still just "slows it down."

[Flybob]

Another link for those that like details.
https://prezi.com/n8f1ymikvmy9/the-e...ust-formation/