Ways to differentiate type of rust
Ways to differentiate type of rust
(OP)
Hi guys,
is there any way to determine the difference between Fe2+ and Fe3+? I don't think telling the difference by the colour of the rust will be reliable enough.
In addition, had anyone heard of black rust from steel? They should be iron oxide which had been oxidized in a high temperature environment. Will a EDX evaluation tell the difference as compare to the normal rust e.g. Fe3+ ?
Thanks guys!
is there any way to determine the difference between Fe2+ and Fe3+? I don't think telling the difference by the colour of the rust will be reliable enough.
In addition, had anyone heard of black rust from steel? They should be iron oxide which had been oxidized in a high temperature environment. Will a EDX evaluation tell the difference as compare to the normal rust e.g. Fe3+ ?
Thanks guys!





RE: Ways to differentiate type of rust
RE: Ways to differentiate type of rust
RE: Ways to differentiate type of rust
RE: Ways to differentiate type of rust
Assuming by "rust" you mean iron oxides- FeO (black) ,forms at highest temperature (> 1300F +/-). Fe3 O4(black) forms at intermediate temps. Fe2 O3 (red) forms at 700F +/-, and at room temp (lookup fretting corrosion). Fe3 O4 -H2O (brown) ambient temp (it can be written with different formula like FeO2(OH)2). Finks Index will give you more pages of compounds than you want and you will find using the mineral names is not straightforward .When using XRD ,keep in mind some have strong crystallinity and give misleading patterns if you are trying to quantify them.
RE: Ways to differentiate type of rust
I agree with blacksmith,the XRD spectrum can give misleading patterns. In my own experience, spinel oxide (FeCrO type oxide) overlaps with the Fe3O4 and Fe2O3.
Just a thought.
RE: Ways to differentiate type of rust
Similarly, potassium ferrocyanide will react with Fe3+.
Large-scale crevice corrosion or "pack rust" is often quite dark in color, similar to millscale. It is also more tenaciously adhered, like millscale. I see it all the time on steel bridges after the "rust" colored surface layers are blasted off.
RE: Ways to differentiate type of rust
I was not aware of the overlap between certain compounds though, so thanks for that - I will quiz the testing people.
RE: Ways to differentiate type of rust
Please give some directions to 'inet'; googling did not turn up very much. Thanks.
RE: Ways to differentiate type of rust
RE: Ways to differentiate type of rust
RE: Ways to differentiate type of rust
Declan