Methanol/Ethanol corroding metals 1

[drodrig]

Hi everyone,

We are planning to use Methanol or Ethanol for cooling (-40ºC/-40ºF minimum temperature).

The problem we are facing (apart from the flammability) is the corrosion. We want to use aluminium pipes because of the good conductivity (copper is not possible for us).

How can we overcome this problem?

We could anodize the aluminium but we have some parts which are plates with holes for the coolant. We might also 3D print some tricky parts with the channels inside.

We could (if really needed) use steel or stainless steel

It seems the Ethanol is less corrosive, so in principle more promising, but also more expensive.

Does anyone have any knowledge about this topic?

Thank you in advance
Regards,

 

[micalbrch]

I would not use aluminum pipes with highly flammable liquids due to danger of ignition. Even slight blows (beats) on aluminum with other metals cause sparks with high ignition potential.

 

[EdStainless]

There are some corrosion inhibitor packages for use in alcohol. The biggest problem is moisture absorption.
You might want to look at stainless steel, it is strong enough that you can use much thinner walls than in Al.

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

 

[SJones]

The steel option might suffer with ethanol/methanol as well:

http://www.techstreet.com/api/products/1377825

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/pub/8/83b/b04

All answers are personal opinions only and are in no way connected with any employer.

 

[moltenmetal]

micalbrch: that's news to me. Do you have a reference for your claim that aluminum is a source of spark ignition?

Aluminum is definitely used in fuel-handling equipment.

Do you have a reference indicating that aluminum isn't compatible with cold methanol? I checked an old copy of the NACE tables I had at hand and it shows < 0.005 in/yr corrosion for either methanol or ethanol, but that table doesn't break down by grade of aluminum. I suspect what you may be worrying about is rather like the concerns with the use of deionized or distilled water- problems that will go away entirely in practical terms in a closed-loop deoxygenated tempered cooling system.

 

[micalbrch]

Molton: I can't say anything concerning chemical resistance of aluminum with methanol/ethanol if that question was also addressed to me. But concerning the use of aluminum in a potentially explosive athmosphere I refer to EN 1227-1, chapter 5.3 and 6.4.4. I can't attach a copy as there is a copyright on the standard. The chapters describe the possible danger of aluminum in combination with rust (on a rusty tool for example).

 

[TomDOT]

Well, Aluminum + (iron) rust = Thermite - but that's very, very difficult to ignite accidentally. I've most often seen it done with magnesium ribbon. Required ignition temperature is something around 1,600C.

 

[SJones]

http://www.bsee.gov/Research-and-Tr...t-and-Research/tarprojects/400-499/405AA.aspx

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/pub/8/83b/b04

All answers are personal opinions only and are in no way connected with any employer.

 

[moltenmetal]

p. 41 of that report says that aluminum-coated steel is only modestly more susceptible to sparking than rusted steel itself when impacted with rusted steel targets. People don't shy away from using STEEL to convey flammable materials, do they?

 

[Ehzin]

Drodrig,

I don't know if you've reached a solution on this but I figured I'd forward some information for you to look into. There was a CSB investigation into a fire that occurred at a Florida plant in 2006. A flame arrestor had experienced corrosion that the investigation found to be due to the methanol service in the tank it was attached to. The final report simply references "NACE International, The Corrosion Society (2002). Corrosion Survey Database (COR·SUR). NACE International." I'd consider reviewing this data for the susceptibility of the corrosion of aluminum in methanol service.