Comparison Between ASTM A127 (MONAL ALLOY400) and ASTM A36

What is there to compare?!?!?!

A36 is plain carbon steel.

[Do you mean ASTM B127 - Monel 400]? which is a nickel alloy.

What is the service? Because there is a HUGE difference between the two.

How do you even make recommendations to clients like this when you don't even have the most basic idea/information about what you are talking about?

Although post # 2 sounds like me, it wasn't.

Still a good point.

You should give the client what they specified. And paid for.

I am assuming as you mention splash zone you are constructing for the offshore industry the client is specifying Monel for corrosion resistance to seawater in the splash-zone / semi submerged area. This is of course where corrosion is most aggressive, and traditional coatings are not particularity effective. Monel (70% Ni- 25% Cu, ++) is extremely resistant to sea water corrosion - which is why it is specified as a "wrap around plate". Standard "mild steel A36" of course has little corrosion resistance to seawater and it would be unlikely that they will accept the substitution. An alternative to wrapping with Monel sheet would be to thermally spray Monel coating over a A36 wrap plate - subject of course to your clients requirements.

Monel 400 has Ni 66%,Cu 32%, Mn 0.9% & Fe 1.35% as major elements it has got high strength and good resistance to corrosion and easily weldable to ferritic and austenitic steels using MMAW, TIG, MIG processes.

Where in, A 36 is a low strength mild steel material and cannot withstand the corrosion atmosphere and temperature, even though it is not directly used to carry the corrosion media.

During the welding of outer jacket, A 36 may come in contact with Monel 400. It is important to remember Ni & Ni alloys are susceptible to embrittlement by accidental presence of lead, sulphur, phosphorus, and low melting metals. Purging may also be required for the Monel tubes during welding to avoid oxidation developed due heat transfer.

Further, during welding, carbon goes into solution and may form carbon precipitation or sensitization in the weld HAZ and may lead to inter-crystalline corrosion at certain service environments in the same manner as in the case of austenitic SS metals. This will reduce the life of your jacket.

Presence of SI in the A36 may also cause hot crackling high Nickel alloy.

If your idea of using it as a outer jacket, you have to consider these factors before determining the change over from Monel to A36 as an outer jacket, even though it is cost effective.

You may land in more problems during service and it will be much more costlier to repair/replace and cumbersome at that time. So, please think over and act.

Sridhar.

No comparison can be held between ASTM A 36 and ASTM B(not A)127-400, where the difference is equal to the difference between the earth and 7th sky.

The attached drawing is an example for lining of nozzle of a heat exchanger fabricated from flange of SA 105 (weld deposited by SB 127) and pipe nozzle of SA 106-B lined from inside by sheets with thickness 3 mm of SB 127 UNS 4400.

............................with

I think you're talking about the protection of the splash zone of an offshore platform. The application of monel is a typical solution for corrosion protection see the doc linked below:

http://www.copper.org/applications/cuni/txt_cuni.html

http://www.copper.org/applications/cuni/pdf/splash_zone_michels_powell.pdf

an alternative to the monel could be carbon steel coated with something like glass flake epoxy of TSA (thermally sprayed aluminum) or you've to plan for manintenance and replacement of the CS plate

S

corrosion & rust protection

All of the above posters are correct, there is no possible comparison between the two. One thing you need to be aware of is that if Cathodic protection is present (It almost always is.) you can get hydrogen embrittlement of the monel.