Will a Needlegun scaler remove mill scale? I've been using a knotted steel wire cup brush on a 9" grinder. It's still taking a lot of time. The pieces (bumpers and rock rails from a 4x4) won't fit in a shot blasting cabinet.
I tired these: http://www.screwfix.com/p/preparation-wheel-115mm/83915
They don't last long, and after a while they were leaving some rubbery residue which I needed to shotblast off (not ideal as I have to shot blast in an open environment as the parts won't fit in a cabinet).
I've also just tried vinegar on a test piece. It's been 4 hours and the mill scale has gone soft. Does I have to neutralise the vinegar, or is a rinse enough?
Praps the disc got too hot? I've not had any residue with them. Or maybe the Screwfix discs aren't great.
I've used citric acid, I think Chunko mentioned about it removing millscale. Makes it a slime that wipes off. I guess a quick rinse is OK with the vinegar, the acid won't be a problem, most of the vinegar will be water, guess there's a v.small chance whatever else is in it might cause a prob with paint.
P80 zirconium flap disc will work fine, but will take a while to do. Would it not be easier to simply get all the parts powder coated, which will include blast cleaning prep work?
Flap disc works. Also not the quickest. I think I've tried all methods now.
1. Prep discs - a little slow, and they wear out quickly. Mine also started leaving a residue that was tougher than the mill scale!
2. Flap discs - work fine. A little unsure about how long they last though.
3. Grinding discs. Work fine, but aggresive
4. Vinegar dip. Works on test pieces. I'm a little concerned that by the time you dip, and then rinse, the metal would have started rusting already. Plus having to dry it all thoroughly in a workshop is not easy.
5. Sand blasting. Slow (even using a Sealey heavy duty gun). However this is the way I've decided to go in the end, as the pitted finish helps adhere the paint.
Now to build a blast cabinet that's big enough to fit a 4x4 bumper!
I didn't try the needle scaler in the end. The manufacturers state that they will remove "loose scale". And no one seems to mention the needle scaler as a method that works. So in the end decided it's not worth the investment to test it.
DeoxyC by bilt hamber removes mill scale a treat.
if the parts are too big to remove and put into soak I have done this.
Wrap the parts in paper towels, soak them with it then wrap in cling film to stop them drying out.
They do make a gel version of it but that costs more.
Needle gun will remove the scale, but will take longer than flap disc on an angle grinder, and you will need to do further finishing work before painting. Simple way to do this job is to get everything powder coated.
Needle gun will remove the scale, but will take longer than flap disc on an angle grinder, and you will need to do further finishing work before painting. Simple way to do this job is to get everything powder coated.
I agree, that all the work and tools - it's just not worth it. Next time I will look at paying the extra for bright steel rather than black steel.
I decided not to go for power coating because the car keeps getting modified (eg will modify the bumper later to fit a winch). Plus bits bend and need to be fixed. And I will have more of these parts to make. So I've decided to invest the time into making a large blast cabinet.