ferrous oxide vs ferric oxde thermite reaction 2

[metman]

In a nutshell; Aluminum impinging on rusty Steel can produce a high energy thermite spark and if in the presence of a certain concentration of Methane gas can result in an explosion.

In the attached whitepaper, page55 – section 4 -- last sentence, “The risk of an ignition is dependent on a number of conditions occurring simultaneously:"

Included in this list of conditions and elsewhere throughout the paper is, “the presence of ferrous oxide.”

I (metman) was curious why ferric oxide was not mentioned. Therefore I did the following searches:

From wikipedia search for iron oxide then clicked on link (Thermite):
Thermites can be a diverse class of compositions. Some "fuels" that can be used include aluminium, magnesium, calcium, titanium, zinc, silicon, and boron and others. One commonly-used fuel in thermite mixtures is aluminium, because of its high boiling point. The oxidizers can be boron(III) oxide, silicon(IV) oxide, chromium(III) oxide, manganese(IV) oxide, iron(III) oxide, iron(II,III) oxide, copper(II) oxide, and lead(II,III,IV) oxide and others.[1]

Metman’s notation:
iron(III) oxide, ferric oxide (Fe203)
iron(II,III) oxide, ferrous oxide (Fe3O4)

From google search for “Thermite reaction aluminum and ferrous oxide” wiki answers or answers.com :
What is the balanced equation for aluminum reacting with iron III oxide to produce aluminum oxide and iron?

Answer:
Fe2O3 + 2Al --> Al2O3 +2 Fe
The reaction is commonly known as thermite for the enormous amount of heat produced. The iron produced by the reaction is molten.

metman's comments:

So it appears to be clear that a thermite reaction between Aluminum and rusty steel could occur whether the rust is composed of ferrous oxide OR ferric oxide.

Again I am curious why ferric oxide was not mentioned in the whitepaper.

Maybe an underground Coal mine environment is much more conducive to produce ferrous oxide vs ferric oxide?

Any comments will be appreciated.


Design for RELIABILITY, manufacturability, and maintainability

 

[metman]

misspelled the second oxIde in the subject line.

Design for RELIABILITY, manufacturability, and maintainability

 

[metman]

Metals handbook, 8th Ed, Vol 1, page 258 text and 259 graph of steel corrosion in underground Coal mine but nothing about actaul corrosion products.

Design for RELIABILITY, manufacturability, and maintainability

 

[metman]

Do the Benefits OutWeigh the Risk ?
or
How to use Aluminum in Underground Coal Mines

This is the title to the whitepaper that did not get attached

Design for RELIABILITY, manufacturability, and maintainability

 

[metengr]

metman;
I reviewed the paper you referenced in your post above. Thermite reaction is common in rail welding and requires a mix of iron oxide and aluminum. This reaction still requires heat by ignition with magnesium foil.

I am not convinced that rusty steel in contact with aluminum will result in a so-called Thermite reaction in an underground mine. I do agree that spark-producing metals should be prohibited from being used. However, to imply that an aluminum metal striking rusty steel could lead to a Thermite reaction is a stretch.
Keep in mind you need two requirements for this type of exothermic reaction; exact stoichiometric quantities between aluminum and iron oxide (rust) and activation energy in the form of heat. My point is a spark that could possibly set off a Thermite reaction would easily result in an explosion given sufficient quantities of methane gas.

 

[unclesyd]

I'll have to disagree somewhat about the probability of producing and a high energy spark by striking.

Though I don't recommend this as a common practice one way to produce a spark is easily demonstrated by striking an Aluminum painted steam trap with a glancing blow. Thing is true with almost all heated carbon steel coated with Al. 90% of the time you will get a very hot spark, even using non-sparking tools. It is now called out in our paint specs that high solids Al paint is not to be used on heated steel in our Intermediates area.
I've have found that a Fe/Al Thermite can be generated with all the oxides of iron the main difference is the energy required to start the process.
One in particular thermite reaction cost us a lot of money. We use tool steel components that have a forced Magnetite surface where we use a self energized Al gasket to seal 600F polymer at 2500 psig. If you use an untreated Al gasket upon initial pressurization at temperature there a Thermite reaction and the two steel parts are welded togather.

 

[metman]

Metengr, You might be willing to reconsider your following comment if you are familiar with Longwall Chocks and if you consider what the paper says about how they were used before hydraulics were implemented:

However, to imply that an aluminum metal striking rusty steel could lead to a Thermite reaction is a stretch.

The following two comments by metengr/unclesyd satisfy my curiosity:

I substituted P-Chem for Thermo at school so this makes reasonable sense to me and possibly explains why Ferric Oxide is not mentioned.

...exact stoichiometric quantities between aluminum and iron oxide (rust)and activation energy in the form of heat.

I've have found that a Fe/Al Thermite can be generated with all the oxides of iron the main difference is the energy required to start the process.

I will be accompanying a Product Support guy, Steve, who will make a presentation on Hydra-Flow to a huge mining company early next month. Steve dug up the whitepaper online as part of the presentation in support of using Aluminum components underground.

Your comments are much appreciated. lps's

Design for RELIABILITY, manufacturability, and maintainability