Any one used brass nuts and bolts for the exhaust clamps?
01-13-2008, 04:55 PM
#1
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Any one used brass nuts and bolts for the exhaust clamps?
It was a real pain in the 
to undo the bolts for the mufflers as they have corroded. Has anyone had stainless or brass nuts and bolts to replace the old ones?
Harry
to undo the bolts for the mufflers as they have corroded. Has anyone had stainless or brass nuts and bolts to replace the old ones?Harry
01-13-2008, 06:17 PM
#3
Drifting
Stainless is good if you can find them, but carbon steel will work just fine too. I just replaced all the nuts and bolts on my entire exhaust system because I had to replace my cat. Brass bolts of that size is used on toilet flanges here
01-13-2008, 06:27 PM
#4
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Use a material that is compatable with the muffler. Galvanic action between dissimilar metals is not a good thing and is exacerbated with water/salt spray etc. If the parts are stainless...use stainless fasteners and clamps.
01-13-2008, 06:47 PM
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Can you explain what happens? I used galvanized steel bolts to secure the strap around the muffler. These steel bolts do not come in actual contact with the muffler itself, but I'm curious as to what may happen.
01-13-2008, 07:44 PM
#6
Three Wheelin'
. . . Shamelessly Stolen from "About.com" !
01-13-2008, 08:08 PM
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You had to ask!!!
I will try to dig up one of the presentations from ASTM or NASC or find a link to post as the subject can get quite detailed. To answer your question briefly....the galvanization is really just a sacrificial coating...(OK I just re-read my post and find it is far from brief and I apologize....anyone not wanting to be bored stiff, if it's not too late for that can just move on) But as I started on this I was thinking of situations with the P-car that you might find relevant such as calcium chloride cindered roadway with water and stainless exhausts etc....anyway here goes...
If you put two dissimilar metals, or alloys in a common electrolyte, and connect them with a voltmeter, it will show an electric current flowing between the two. (This is how the battery in your automobile works). When the current flows, material will be removed from one of the metals or alloys ( the ANODIC one) and dissolve into the electrolyte. The other metal (the CATHODIC one) will be protected. Or another example for those with metal (not a dentist so I dont know the exact term) fillings and take a fork which contacts the two metals and the fork being made of a different metal than the fillings, add the saliva, and presto!!! You have a current between them and can sometimes actually feel the tingle.
A girl in my metals class in college actually asked the prof if that was how the circus clowns light up those lightbulbs when they place them in their mouths .....but thats another story.
I will post a Galvanic Series chart at the end here. The further apart the materials are located on this chart, the more likely that the one on the ANODIC end will corrode if they are both immersed in any fluid considered to be an electrolyte.
Salt water, is one of the best!
Example #1.
A ship has lots of bronze fittings and a steel hull. Note that steel is located seven lines from the ANODIC end, and bronze is listed at twenty seven rows from the same end. Sea water is a perfect electrolyte, so the bronze fittings would immediately attack the steel hull unless something could be done to either protect the steel ,or give the bronze something else to attack.
The classic way to solve this problem is to attach sacrificial zinc pieces to the hull and let the bronze go after them. Again, looking at the chart, you'll note that zinc is found on line three from the top of the chart. In other words the zinc is further away from the bronze than the iron, so the galvanic action takes place between the zinc and the bronze, rather than between the steel and the bronze. Zinc paint is used for the same reason.
Example #2
Nickel base tungsten carbide contains active nickel. When this face material is used in dual seal applications it is common to circulate water or antifreeze between the seals (as mentioned in the beginning of this paper, water can be an excellent electrolyte because of the addition of chlorine and fluorine). You'll note that active nickel is located twenty one rows from the top of the chart. Passivated 316 stainless steel is positioned nine rows from the bottom. This means that the stainless steel can attack the nickel in the tungsten carbide causing it to corrode.
The rate at which corrosion takes place is determined by :
The distance separating the metals on the galvanic series chart
The temperature and concentration of the electrolyte. The higher the temperature, the faster it happens. Any stray electrical currents in the electrolyte will increase the corrosion also.
The relative size of the metal pieces. A large cross section piece will not be affected as much as a smaller one.
Many metal seal components are isolated from each other by the use of rubber o-rings or similar materials and designs. Shaft movement that causes fretting of the 316 stainless steel rubs off the passivated layer and exposes the active stainless to the electrolyte until the metal part becomes passivated once more. This is one of the reasons we see corrosion under o-rings, and Teflon wedges.
Pitting is an accelerated form of chemical attack in which the rate of corrosion is greater in some areas than others. It occurs when the corrosive environment penetrates the passivated film in only a few areas as opposed to the overall surface. As stated earlier, halogens will penetrate passivated stainless steel. Referring to the galvanic chart you'll note that passivated 316 stainless steel is located nine lines from the bottom and active 316 stainless steel is located thirteen lines from the top. Pit type corrosion is therefore simple galvanic corrosion, occuring as the small active area is being attacked by the large passivated area. This difference in relative areas accelerates the corrosion, causing the pits to penetrate deeper. The electrolyte fills the pits and prevents the oxygen from passivating the active metal so the problem gets even worse. This type of corrosion is often called "Concentrated cell corrosion". You'll also see it under rubber parts that keep oxygen away from the active metal parts, retarding the metal's ability to form the passivated layer.
INTERGRANULAR CORROSION
All austenitic stainless steels (the 300 series, the types that "work harden") contain a small amount of carbon in solution in the austenite. Carbon is precipitated out at the grain boundaries, of the steel, in the temperature range of 1050° F. (565° C) to 1600° F. (870° C.). This is a typical temperature range during the welding of stainless steel.
This carbon combines with the chrome in the stainless steel to form chromium carbide, starving the adjacent areas of the chrome they need for corrosion protection. In the presence of some strong corrosives an electrochemical action is initiated between the chrome rich and chrome poor areas with the areas low in chrome becoming attacked. The grain boundaries are then dissolved and become non existent. There are three ways to combat this:
Anneal the stainless after it has been heated in this sensitive range. This means bringing it up to the proper annealing temperature and then quickly cooling it down through the sensitive temperature range to prevent the carbides from forming.
When possible use low carbon content stainless if you intend to do any welding on it. A carbon content of less than 0.3% will not precipitate into a continuous film of chrome carbide at the grain boundaries. 316L is as good example of a low carbon stainless steel.
Alloy the metal with a strong carbide former. The best is columbium, but sometimes titanium is used. The carbon will now form columbium carbide rather than going after the chrome to form chrome carbide. The material is now said to be "stabilized"
CHLORIDE STRESS CORROSION.
If the metal piece is under tensile stress, either because of operation or residual stress left during manufacture, the pits mentioned in a previous paragraph will deepen even more. Since the piece is under tensile stress cracking will occur in the stressed piece. Usually there will be more than one crack present causing the pattern to resemble a spider's web. Chloride stress cracking is a serious problem in industry and not often recognized by the people involved. In the seal business it is a serious problem if you use stainless steel springs or stainless steel bellows in your seals. This is the main reason that Hastelloy C is recommended for spring material. Here are some additional thoughts about chloride stress cracking that you'll want to consider:
Chlorides are the big problem when using the 300 series grades of stainless steel. The 300 series is the one most commonly used in the process industry because of its good corrosion resistant proprieties. Outside of water, chloride is the most common chemical found in nature and remember that the most common water treatment is the addition of chlorine.
Beware of insulating or painting stainless steel pipe. Most insulation contains chlorides and piping is frequently under tensile stress. The worst condition would be insulated, steam traced, stainless steel piping. If it's necessary to insulate stainless steel pipe, a special chloride free insulation can be purchased, or the pipe can be coated with a protective film prior to insulating.
Stress cracking can be minimized by annealing the metal, after manufacture, to remove residual manufactured stresses.
Never replace a carbon steel bolt with a stainless steel one unless you're sure there are no chlorides present. Bolts can be under severe tensile stress.
No one knows the threshold values for stress cracking to occur. We only know that you need tensile stress, chlorides, temperature and the 300 series of stainless steel. We do not know how much chloride, stress or temperature.
A friend had trouble with breaking stainless steel fishing hooks while fishing in salt water in the keys....there is the answer to that.
Many cleaning solutions and solvents contain chlorinated hydrocarbons. Be careful using them on or near stainless steel. Sodium hypochlorite, chlorethene. methylene chloride and trichlorethane are just a few in common use. The most common cleaner used with dye checking material is trichloroethane, explaining the reason you sometimes will see cracks after you would weld stainless steel and dye check it to inspect the quality of the weld.
Here is the chart:
CORRODED END ( ANODIC OR LEAST NOBLE)
MAGNESIUM
MAGNESIUM ALLOYS
ZINC
ALUMINUM 5052, 3004, 3003, 1100, 6053
CADMIUM
ALUMINUM 2117, 2017, 2024
MILD STEEL (1018), WROUGHT IRON
CAST IRON, LOW ALLOY HIGH STRENGTH STEEL
CHROME IRON (ACTIVE)
STAINLESS STEEL, 430 SERIES (ACTIVE)
302, 303, 304, 321, 347, 410,416, STAINLESS STEEL (ACTIVE)
NI - RESIST
316, 317, STAINLESS STEEL (ACTIVE)
CARPENTER 20CB-3 STAINLESS (ACTIVE)
ALUMINUM BRONZE (CA 687)
HASTELLOY C (ACTIVE) INCONEL 625 (ACTIVE) TITANIUM (ACTIVE)
LEAD-TIN SOLDERS
LEAD
TIN
INCONEL 600 (ACTIVE)
NICKEL (ACTIVE)
60 NI-15 CR (ACTIVE)
80 NI-20 CR (ACTIVE)
HASTELLOY B (ACTIVE)
BRASSES
COPPER (CA102)
MANGANESE BRONZE (CA 675), TIN BRONZE (CA903, 905)
SILICONE BRONZE
NICKEL SILVER
COPPER - NICKEL ALLOY 90-10
COPPER - NICKEL ALLOY 80-20
430 STAINLESS STEEL
NICKEL, ALUMINUM, BRONZE (CA 630, 632)
MONEL 400, K500
SILVER SOLDER
NICKEL (PASSIVE)
60 NI- 15 CR (PASSIVE)
INCONEL 600 (PASSIVE)
80 NI- 20 CR (PASSIVE)
CHROME IRON (PASSIVE)
302, 303, 304, 321, 347, STAINLESS STEEL (PASSIVE)
316, 317, STAINLESS STEEL (PASSIVE)
CARPENTER 20 CB-3 STAINLESS (PASSIVE), INCOLOY 825
NICKEL - MOLYBDEUM - CHROMIUM - IRON ALLOY (PASSIVE)
SILVER
TITANIUM (PASS.) HASTELLOY C & C276 (PASSIVE), INCONEL 625(PASS.)
GRAPHITE
ZIRCONIUM
GOLD
PLATINUM
PROTECTED END (CATHODIC OR MOST NOBLE)
I will try to dig up one of the presentations from ASTM or NASC or find a link to post as the subject can get quite detailed. To answer your question briefly....the galvanization is really just a sacrificial coating...(OK I just re-read my post and find it is far from brief and I apologize....anyone not wanting to be bored stiff, if it's not too late for that can just move on) But as I started on this I was thinking of situations with the P-car that you might find relevant such as calcium chloride cindered roadway with water and stainless exhausts etc....anyway here goes...
If you put two dissimilar metals, or alloys in a common electrolyte, and connect them with a voltmeter, it will show an electric current flowing between the two. (This is how the battery in your automobile works). When the current flows, material will be removed from one of the metals or alloys ( the ANODIC one) and dissolve into the electrolyte. The other metal (the CATHODIC one) will be protected. Or another example for those with metal (not a dentist so I dont know the exact term) fillings and take a fork which contacts the two metals and the fork being made of a different metal than the fillings, add the saliva, and presto!!! You have a current between them and can sometimes actually feel the tingle.
A girl in my metals class in college actually asked the prof if that was how the circus clowns light up those lightbulbs when they place them in their mouths .....but thats another story.
I will post a Galvanic Series chart at the end here. The further apart the materials are located on this chart, the more likely that the one on the ANODIC end will corrode if they are both immersed in any fluid considered to be an electrolyte.
Salt water, is one of the best!
Example #1.
A ship has lots of bronze fittings and a steel hull. Note that steel is located seven lines from the ANODIC end, and bronze is listed at twenty seven rows from the same end. Sea water is a perfect electrolyte, so the bronze fittings would immediately attack the steel hull unless something could be done to either protect the steel ,or give the bronze something else to attack.
The classic way to solve this problem is to attach sacrificial zinc pieces to the hull and let the bronze go after them. Again, looking at the chart, you'll note that zinc is found on line three from the top of the chart. In other words the zinc is further away from the bronze than the iron, so the galvanic action takes place between the zinc and the bronze, rather than between the steel and the bronze. Zinc paint is used for the same reason.
Example #2
Nickel base tungsten carbide contains active nickel. When this face material is used in dual seal applications it is common to circulate water or antifreeze between the seals (as mentioned in the beginning of this paper, water can be an excellent electrolyte because of the addition of chlorine and fluorine). You'll note that active nickel is located twenty one rows from the top of the chart. Passivated 316 stainless steel is positioned nine rows from the bottom. This means that the stainless steel can attack the nickel in the tungsten carbide causing it to corrode.
The rate at which corrosion takes place is determined by :
The distance separating the metals on the galvanic series chart
The temperature and concentration of the electrolyte. The higher the temperature, the faster it happens. Any stray electrical currents in the electrolyte will increase the corrosion also.
The relative size of the metal pieces. A large cross section piece will not be affected as much as a smaller one.
Many metal seal components are isolated from each other by the use of rubber o-rings or similar materials and designs. Shaft movement that causes fretting of the 316 stainless steel rubs off the passivated layer and exposes the active stainless to the electrolyte until the metal part becomes passivated once more. This is one of the reasons we see corrosion under o-rings, and Teflon wedges.
Pitting is an accelerated form of chemical attack in which the rate of corrosion is greater in some areas than others. It occurs when the corrosive environment penetrates the passivated film in only a few areas as opposed to the overall surface. As stated earlier, halogens will penetrate passivated stainless steel. Referring to the galvanic chart you'll note that passivated 316 stainless steel is located nine lines from the bottom and active 316 stainless steel is located thirteen lines from the top. Pit type corrosion is therefore simple galvanic corrosion, occuring as the small active area is being attacked by the large passivated area. This difference in relative areas accelerates the corrosion, causing the pits to penetrate deeper. The electrolyte fills the pits and prevents the oxygen from passivating the active metal so the problem gets even worse. This type of corrosion is often called "Concentrated cell corrosion". You'll also see it under rubber parts that keep oxygen away from the active metal parts, retarding the metal's ability to form the passivated layer.
INTERGRANULAR CORROSION
All austenitic stainless steels (the 300 series, the types that "work harden") contain a small amount of carbon in solution in the austenite. Carbon is precipitated out at the grain boundaries, of the steel, in the temperature range of 1050° F. (565° C) to 1600° F. (870° C.). This is a typical temperature range during the welding of stainless steel.
This carbon combines with the chrome in the stainless steel to form chromium carbide, starving the adjacent areas of the chrome they need for corrosion protection. In the presence of some strong corrosives an electrochemical action is initiated between the chrome rich and chrome poor areas with the areas low in chrome becoming attacked. The grain boundaries are then dissolved and become non existent. There are three ways to combat this:
Anneal the stainless after it has been heated in this sensitive range. This means bringing it up to the proper annealing temperature and then quickly cooling it down through the sensitive temperature range to prevent the carbides from forming.
When possible use low carbon content stainless if you intend to do any welding on it. A carbon content of less than 0.3% will not precipitate into a continuous film of chrome carbide at the grain boundaries. 316L is as good example of a low carbon stainless steel.
Alloy the metal with a strong carbide former. The best is columbium, but sometimes titanium is used. The carbon will now form columbium carbide rather than going after the chrome to form chrome carbide. The material is now said to be "stabilized"
CHLORIDE STRESS CORROSION.
If the metal piece is under tensile stress, either because of operation or residual stress left during manufacture, the pits mentioned in a previous paragraph will deepen even more. Since the piece is under tensile stress cracking will occur in the stressed piece. Usually there will be more than one crack present causing the pattern to resemble a spider's web. Chloride stress cracking is a serious problem in industry and not often recognized by the people involved. In the seal business it is a serious problem if you use stainless steel springs or stainless steel bellows in your seals. This is the main reason that Hastelloy C is recommended for spring material. Here are some additional thoughts about chloride stress cracking that you'll want to consider:
Chlorides are the big problem when using the 300 series grades of stainless steel. The 300 series is the one most commonly used in the process industry because of its good corrosion resistant proprieties. Outside of water, chloride is the most common chemical found in nature and remember that the most common water treatment is the addition of chlorine.
Beware of insulating or painting stainless steel pipe. Most insulation contains chlorides and piping is frequently under tensile stress. The worst condition would be insulated, steam traced, stainless steel piping. If it's necessary to insulate stainless steel pipe, a special chloride free insulation can be purchased, or the pipe can be coated with a protective film prior to insulating.
Stress cracking can be minimized by annealing the metal, after manufacture, to remove residual manufactured stresses.
Never replace a carbon steel bolt with a stainless steel one unless you're sure there are no chlorides present. Bolts can be under severe tensile stress.
No one knows the threshold values for stress cracking to occur. We only know that you need tensile stress, chlorides, temperature and the 300 series of stainless steel. We do not know how much chloride, stress or temperature.
A friend had trouble with breaking stainless steel fishing hooks while fishing in salt water in the keys....there is the answer to that.
Many cleaning solutions and solvents contain chlorinated hydrocarbons. Be careful using them on or near stainless steel. Sodium hypochlorite, chlorethene. methylene chloride and trichlorethane are just a few in common use. The most common cleaner used with dye checking material is trichloroethane, explaining the reason you sometimes will see cracks after you would weld stainless steel and dye check it to inspect the quality of the weld.
Here is the chart:
CORRODED END ( ANODIC OR LEAST NOBLE)
MAGNESIUM
MAGNESIUM ALLOYS
ZINC
ALUMINUM 5052, 3004, 3003, 1100, 6053
CADMIUM
ALUMINUM 2117, 2017, 2024
MILD STEEL (1018), WROUGHT IRON
CAST IRON, LOW ALLOY HIGH STRENGTH STEEL
CHROME IRON (ACTIVE)
STAINLESS STEEL, 430 SERIES (ACTIVE)
302, 303, 304, 321, 347, 410,416, STAINLESS STEEL (ACTIVE)
NI - RESIST
316, 317, STAINLESS STEEL (ACTIVE)
CARPENTER 20CB-3 STAINLESS (ACTIVE)
ALUMINUM BRONZE (CA 687)
HASTELLOY C (ACTIVE) INCONEL 625 (ACTIVE) TITANIUM (ACTIVE)
LEAD-TIN SOLDERS
LEAD
TIN
INCONEL 600 (ACTIVE)
NICKEL (ACTIVE)
60 NI-15 CR (ACTIVE)
80 NI-20 CR (ACTIVE)
HASTELLOY B (ACTIVE)
BRASSES
COPPER (CA102)
MANGANESE BRONZE (CA 675), TIN BRONZE (CA903, 905)
SILICONE BRONZE
NICKEL SILVER
COPPER - NICKEL ALLOY 90-10
COPPER - NICKEL ALLOY 80-20
430 STAINLESS STEEL
NICKEL, ALUMINUM, BRONZE (CA 630, 632)
MONEL 400, K500
SILVER SOLDER
NICKEL (PASSIVE)
60 NI- 15 CR (PASSIVE)
INCONEL 600 (PASSIVE)
80 NI- 20 CR (PASSIVE)
CHROME IRON (PASSIVE)
302, 303, 304, 321, 347, STAINLESS STEEL (PASSIVE)
316, 317, STAINLESS STEEL (PASSIVE)
CARPENTER 20 CB-3 STAINLESS (PASSIVE), INCOLOY 825
NICKEL - MOLYBDEUM - CHROMIUM - IRON ALLOY (PASSIVE)
SILVER
TITANIUM (PASS.) HASTELLOY C & C276 (PASSIVE), INCONEL 625(PASS.)
GRAPHITE
ZIRCONIUM
GOLD
PLATINUM
PROTECTED END (CATHODIC OR MOST NOBLE)
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nveeser (01-24-2022)
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01-13-2008, 08:12 PM
#8
Drifting
The galvinzed surface will likely 'give itself up' first. Once it's gone, there may be corrosion happening. Cadmium coated hardware would be excellent in this application too...
01-13-2008, 09:56 PM
#10
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I recommend SS bolts with silicon-bronze nuts (and si-br lockwashers, if required). That is what I used to enable an easy swap between the cat-bypass and the cat when I had to present my 84 Carrera 3.2 for its annual smog test here in BC. I'm using this kind of hardware now on my 993 after removing the right side muffler to replace the spark plugs. I researched this on the Pelican site some years ago, and there appeared to be a consensus that the stainless/silicon-bronze combination was a preferred and cost effective solution. It worked for me.
Last edited by RSRee; 01-13-2008 at 09:57 PM. Reason: spelling, what else ...
01-14-2008, 12:41 PM
#11
Race Director
Where did you get them? Is there a particular type of store that sells them? I've looked at Home Depot in the past and they have the SS hardware (in SAE sizes, not metric) but not the nuts. I would love to get both in metric for the 993.
01-14-2008, 02:58 PM
#13
Race Director
01-14-2008, 07:21 PM
#14
Rennlist Member
Thread Starter
I recommend SS bolts with silicon-bronze nuts (and si-br lockwashers, if required). That is what I used to enable an easy swap between the cat-bypass and the cat when I had to present my 84 Carrera 3.2 for its annual smog test here in BC. I'm using this kind of hardware now on my 993 after removing the right side muffler to replace the spark plugs. I researched this on the Pelican site some years ago, and there appeared to be a consensus that the stainless/silicon-bronze combination was a preferred and cost effective solution. It worked for me.
Harry
01-14-2008, 08:05 PM
#15
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In fact I just checked the link to be sure it was working, and they do mail-order, even small quantities. Be sure to download their on-line cataloque, which is a large pdf file.
Last edited by RSRee; 01-14-2008 at 08:19 PM. Reason: more info ...