Hi @discostew,
Thank you for your question and welcome to the Bunnings Workshop community, it is fantastic to have you with us.
I've done a lot of work with steel framing systems and can tell you that they are not as strong as you would expect when studs are used in isolation. They get most of their strength from being connected into one whole wall unit where the weight is distributed between multiple studs.
I'm glad that you've been cautious with this sort of installation as while the bracket is suited to supporting the TV's weight, at a load centre of 1m, the weight of the TV will be amplified considerably.
Generally, when mounting to steel studs, during the construction stage, timber will be added to the channel of the stud because timber studs are far better at supporting a load than steel studs are.
Unfortunately, unless you can identify the specific steel framing system that was used, it would be very difficult to say whether the stud would be able to support the load applied to it or not.
I'd suggest cutting a patch out of the gyprock using a Wallboard Saw and attaching some pine framing to the cement wall using 100mm DynaBolts. This timber will act as a mounting block that will transfer the load of the TV through the Dynabolts and into the cement wall which will be more than adequate to support the load.
Once this timber block is in place, reinstate the gyprock patch, plaster the joins using a Gyprock CSR 1.5kg DIY Rapid Plaster Repair Kit, and paint to match the surrounding wall.
Now the gyprock has been patched and painted, attach the TV mount to the timber block using the hardware you received with the TV mounting bracket.
Let me know what you think and if you have any further questions, I would be happy to offer further assistance if required.
Jacob
