First, do you know the brace is magnetized? Being essentially a long bar, it could be, but maybe not. I don't know the steel used, but mild steel does not hold magnetism at all. It can be pulled toward a magnet, but it can not be made to act as a magnet.
Remember, the compass itself is a magnet.
I took a good quality hand compass and moved it close to each end of my soon to be installed brace and it only responded to the lower end--perhaps the flat piece is magnetized, but the tube was not and the compass did not respond to the tube at all.
Take a paper clip, hang it from a thread and move it close to each end of the brace. If it moves to the brace when it is close, then it does need to be demagnetized.
If you are installing a compass on the brace, the safest place is midway, where the poles neutralize each other.