Date:         Tue, 21 Aug 2007 19:52:21 +0000
Reply-To:     rubatoguy@COMCAST.NET
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Todd Last <rubatoguy@COMCAST.NET>
Subject:      Re: exhaust nuts & bolts is 304, 308, 309, 316 or zinc plated etc
Comments: To: TC <trclark@SHAW.CA>

I thought that the use of copper or brass nuts were the way to go with exhaust systems - since they will not rust to the metal.  If you are using stanless, make sure the fasteners are of the correct grade - steer clear of the hardware store stanless steel fasteners which tend to alwasy be of the lowest grade.

Todd

"Alloy Classes
Before considering corrosion resistance as a selection requirement, a review of the stainless steel and high temperature alloy classes may be helpful.

The simplest stainless steels contain a minimum of about 11% chromium, in addition to iron. They are generally known as the AISI 400 series of stainless steels. Depending on the chromium and carbon contents, they may be martensitic or ferritic. The martensitic alloys, typically containing more than 0.08% carbon, are hardenable by heat treatment. Type 410 stainless is a typical grade.

Increasing chromium or reducing carbon results in a ferritic stainless steel, which is non-hardenable by heat treatment. Type 430 stainless is a typical alloy in this family. Increasing chromium also improves corrosion resistance. Therefore, Type 430 stainless (18% chromium) is more corrosion resistant than Type 410 stainless (12% chromium).

For more significant improvement in corrosion resistance, a switch to the AISI 300 series is required. Nickel is the important alloying element in the 300 series, which includes types such as Custom Flo 302HQ, 304 and 305 stainless steels.

These grades are the 18-8 stainless steels, containing about 18% chromium and a minimum of 8% nickel. They are austenitic and nonhardenable by heat treatment, but do work-harden by cold working. Molybdenum may be added for greater resistance to chloride pitting (Type 316). Still other alloying elements may be added to enhance the alloys' fabrication characteristics. For example, Custom Flo 302HQ contains 3 to 4% copper, which lowers the alloy's work hardening rate and thus improves headability.

Another stainless steel category covers the age-hardening or precipitation-hardening alloys such as Carpenter Custom 450® stainless, Custom 455® stainless and Custom 630® (17Cr-4Ni) stainless. They provide corrosion resistance at a strength level unavailable in the 300 or 400 series stainless steels.

A separate group comprises the high temperature alloys. Included in this classification are grades such as Pyromet® Alloy 718, Pyromet Alloy A-286 and Waspaloy. These alloys, like the precipitation-hardening grades, involve much more specialized heading techniques and require considerably more energy to head.

Another material used in specialized applications is Carpenter Ni-Cu Alloy 400. This is an alloy with relatively high strength and toughness over a wide temperature range. Ni-Cu Alloy 400, with its very low work hardening rate, is easy to head."


 -------------- Original message ----------------------
From: TC <trclark@SHAW.CA>
> 85 1.9 gl
> So i am confused here what really works after 4-5 year when time to r&r the
> exhaust again
>
> I tried some 304 ss 12 mths ago for the tail pipe connected to the muffler
> with anti-seize
> ( the 1800F copper stuff)
> so for shits & giggle when my connector pipe went the other day I thought
> I'd see how easy
> the 3 304 ss bolts come off well they wont come off.. well really easy any
> ways with a socket wrench
> so I guess I have what they call galling occurring when the ss has heated up
> & come off & bonded to the steel
> thread in the muffler...
>
> So now when i do the connector pipe what grade of ss do i use 304 is out so
> 3XX or zinc plated ??
> I will try the 2400F nickle based anti-seize
> http://www.permatex.com/documents/tds/automotive/77164.pdf
> http://www.jmindsupply.com/permatex-nickel%20antiseize%20lubricant.htm