Niles H.

953 seems like an excellent frame material; but there is apparently an issue with increased susceptibility to corrosion once it has been heated beyond a certain point.

Are there ways around this?

Are there low-temperature options that avoid the problem?

Other solutions?

Nessism

What is the source of this concern?

Falanx

Well, metallurgy, for a start....

Soil_Sampler

Sounds like a question for Reynolds?

https://www.frameforum.net/953-FAQs1.pdf

Nessism

If you have first hand knowledge about problems with corrosion on 953 due to brazing please share. Keep in mind that this is a framebuilders forum, not a metallurgy forum, so please use terms we can understand.

My understanding is that 953 has not been very well received in the framebuilding community due to various reason; high cost, heat treatment concerns, and out of specification tubes being just a few. I've never heard about corrosion issues though other than what was posted in Reynold's FAQ's linked above.

Falanx

Not on 953 as a product, but on the alloy the tubing is drawn from, yes.

Carpenter Custom 455 is a very low chromium corrosion resistant alloy. It is developed from the old 1950-era maraging steels that were made with nickel. They rusted at about half the normal rate of most low alloy steels.

The design of 'stainless' (only just, an in a very small range of slightly corrosive environments) maraging steels is a careful balancing act between providing them corrosion resistance and still having a composition amenable to age hardening.

You're unlikely to hear much in the way of corrosion references from Reynolds for two reasons:
1.) C455 is normally a forging stock. It's rarely welded or brazed, so very few manufacturers even think about the effect of prolonged heating on chromium-rich steels. Few know, few are concerned. It doesn't affect them.

2.) Reynolds have shown their lack of understanding of the base materials in all stages of production and marketing. It's unlikely they would consider the reaction of chromium-rich steels to prolonged heating in certain temperature ranges.

There is a temperature range for almost all corrosion-resistant maraging steels which is very deleterious. That temperature range starts at about 540 degrees. Beyond about 620 degrees the steel reverts to austenite, which undoes the heat treatment anyway.

On top of that, prolonged heating in the aging temperature range (about 480 degrees) causes overaging, with it's own alteration in the corrosion resistance of the steel.

Complex multicomponent silver solders tend to melt at lower temperatures than copper or nickel rich alloys, and their specific heat is lower, which in turn means less heat exposure for the tubing.

I know it's framebuilders forum, Nessism, I have been a contributor here long enough...

Thylacine

The tubes are mostly being sold in their aged state now, and the majority of people using the stuff are silver brazing it, which negates any of these problems.

Lord knows what happens when you weld the stuff with the wrong filler, and what that does to the corrosion resistance in the HAZ.

Falanx

First, a slight brown discoloration... followed by some ugly looking pitting.

Then, as unstoppable as the wrath of kings, your rear triangle will part company with your fore, and your bum will part company with yopur saddle.... Or words to that effect.

If taken care of, then such a frame can be protected, as long as one is not averse to rubbing the frame with a scotchpad and a little oxalic acid. But you have to be aware it will happen, and there's not much you can do about it. Remember to hose it down properly if you've been out riding in winter, and dry it out indoors as soon as you can. Strong salt solutions hurt most stainlesses, but those at the 10-13% Cr content are particularly badly affected by it.

NoReg

- Falanx.

I got a lot out of that.

Falanx

- Peter.

No problem ;-)

cujet

What about nickel plating? While I have never knowingly used this alloy, I do nickel plate just about everything I fabricate. Sometimes there is a nickel or chrome plating discoloration at a weld that is due to filler rod alloy differences but rarely any corrosion.

Plating the inside could be possible too.

Chris

Falanx

You nickel plate it, you will make corrosion once the nickel is locally removed via a scratch worse, not better. Nickel plating baths tend to be reducing acids, in which case you will activate the steel below the plating, not passivate it.

Coupled with that, plating is a competition reaction - you will leach out alloying ingredients from the steel surface as you replace them with nickel. The nickel plate will be fairly hard, as is usual, but sandwiched between the hard, brittle nickel plate and the hard, tough steel will be a layer of softened austenite from the extra nickel absorbed into the steel surface. Not good for fatigue....

cujet

Falanx,

I am not in a position to dispute anything you said. However, plating shops that know what they are doing, plate the high end race car suspension components and aircraft structural components I weld. They are not a point of failure. Nor is the plating anything but good for the corrosion protection and overall lifespan. In practice, a nick or scratch is not an issue, using silver paint will protect the scratch and match well enough.

I wonder about electroless nickel plating, can it help reduce the above mentioned issues if they are truly critical in a bicycle application?



Chris

Falanx

Electroless nickel plating is the least corroive method of the lot. But phosphorus and steel are incompatible - and electorless nickel co-deposits between 2 and 6 percent phosphorus.

The assertion that nickel plating is nothing but good is false if it's going down on a normal low alloy steel. Nickel is less reactive than most steels, including activated stainless steels. While it's not a point of failure (generally) is car parts or aircraft parts, it's also not usual to find said parts up to their bottom bracket in mud full of grit.

From a total cost point-of-view, the cheapest method for maintaining corrosion resistance in 953 is to source the right filler wire (the nice thing about the alloy that 953 is made from is that it's a very low carbon steel in the first place, so any C455 wire will be acceptable to fill with, you don't have to source a special filler wire), and then have the assembled frame passivated in a 50% nitric acid bath.

cujet

Cool,

Thanks for the info.

Thylacine

Isn't it kinda stupid to plate something that's supposed to have adequate corrosion resistance anyway? Especially when the biggest issue towards improving the corrosion resistance, is not using incorrect mating materials!?

I've plated quite a few different materials in my time, mostly using electrode-less nickel. Ironically, I've had better luck plating Aluminium than steel, and a handful of 6061 trails frames we built 5-6 years ago are still going strong today, which is unheard of for Trials frames. When I did some work with another frame company, we did a batch of plated Dedacciai EOM XC frames that all developed rust under the plating, and nobody could figure out why and the plater eventually called in damage control and said 'no more frames', so that went out the window.

Now, when we're looking for supreme corrosion resistance externally, we go with ceramics, and internally we use a wax based spray and soak the interior. So far for us, that's the been the best solution.

Falanx

Warwick! Shhh! Stop giving away the trade secrets ;-)

Yeah, that'll be the acid phosphorus in the elctroless nickel. It's a ***** on iron.