Of all the M

n

+1

AX

n

phases

the most resistant to oxidation in air in the 900–1

400°C temperature range are Ti

2

AlC

Ti

3

AlC

2

and Cr

2

AlC. A literature review

however

shows that whil

e many claim the oxidation kinetics to be parabolic

others claim them to be cubic. Whether the kinetics are parabolic or better is of vital practical importance. By carefully re-plotting the results of others and carrying out one oxidation run for ≈3

000 h at 1

200°C on a Ti

2

AlC sample

we conclude that the oxidation kinetics are better described by cubic kinetics and that even that conclusion is an approximation. Lastly

we present compelling evidence that the rate-limiting step during the oxidation of Ti

2

AlC is diffusion down the alumina scale grain boundaries.