Mill scale

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I know I have to grind it off where I'm welding, but do I have to get it all off before painting. Please tell me I don't - there's a fair bit of it.Scott
Reply:I only bother removing it if its a critical weld.  If Im using 6011 I dont bother.  If its thinner than 1/4 inch I wouldnt bother...Im sorry I cant remember the metric conversion..I assume aus uses cm's.   For painting,  Id say clean it up if its real heavy..but I wouldnt bother going to bare metal clean metal...just use a primerGOOD luckIF it Catches...Let it Burn
Reply:BTW whst time is it there?Its 6:37 p.m.  Sunday April 9th IF it Catches...Let it Burn
Reply:It's 25mm (1 inch) square sections in lengths up to 3 metres. I need to make an outdoor bench frame.I might give it all a light sand and use a 2 pack epoxy undercoat - got some in the shed.I did a search and muriatic acid was recommended, but I'd need a bath.Scott
Reply:no no no...like I said dont mess with the light stuff, just take off the heavy stuffIF it Catches...Let it Burn
Reply:I know I have to grind it off where I'm welding, but do I have to get it all off before painting. Please tell me I don't - there's a fair bit of it.
Reply:Thanks. I'll hit it with something just to get any loose or heavy stuff off. Tx,When it's evening there, it's morning of the following day. So your Sunday evening is our Monday morning. Of course, there are several time zones across the US and the same number across Australia. And then when it's afternoon here, you're all asleep - imagine the posts I could make while moderator Smithboy is tucked up in bed.Our share maket is very much driven by the US. Wall street closes at 6am Sydney time, which is handy for people trading the Aussie market. If the US market has been hit badly, we know it's going to be a wobbly start when our market opens 4 hours later. Scott
Reply:I use a 55 gallon barrel and mix up three parts water and one part muretic acid to clean the scale off hot rolled.  It works pretty fast and lasts a long time.  Clean the metal before you fab.  If you want to clean long pieces, cap a long piece of pvc pipe and mount at an angle,  fill with the acid solution and soak in that.  Be sure and rinse well.  You will get rust very quickly, but after fab, I use ospho before priming for paint.
Reply:That capped PVC pipe is a great idea for a bath.
Reply:Oh, and it's 1.40 Monday afternoon in Sydney.Scott
Reply:Great suggestions for the baths, but what I want ot know is what is ospho?    Some sort of phosphate finish or what.  As you can tell I'm new to some of these fab techniques.   for the most part the frames and sutff we have fabed for use at work are just painted over apparently like tex suggests.   This works really good if you don't expect a fancy finish.   The paint does seem to stick really well to te mill scale, in fact better than the primed & painted raw surfaceWhat I'm wondering also is if anybody has made use of body filler to smooth out the mill surface instead of trying ot strip it off?    After weld up of course.    This would seem like the fast way to a really nice finish when needed.Thanksdave Originally Posted by riley mcmillan..... I use ospho before priming for paint.
Reply:Great suggestions for the baths, but what I want ot know is what is ospho? Some sort of phosphate finish or what.
Reply:I would like to clarify about the 55 gallon barrel.  It is that blue plastic barrel that impervious to acid.  That muretic acid will eat up a steel barrel.  I'm sure most people already know that.
Reply:Originally Posted by wizardGreat suggestions for the baths, but what I want ot know is what is ospho?    Some sort of phosphate finish or what.  As you can tell I'm new to some of these fab techniques.   for the most part the frames and sutff we have fabed for use at work are just painted over apparently like tex suggests.   This works really good if you don't expect a fancy finish.   The paint does seem to stick really well to te mill scale, in fact better than the primed & painted raw surfaceWhat I'm wondering also is if anybody has made use of body filler to smooth out the mill surface instead of trying ot strip it off?    After weld up of course.    This would seem like the fast way to a really nice finish when needed.Thanksdave
Reply:Having had a few boats, I also often use marine paint. It's more expensive, but it's fantastic to paint with and gives a great finish. It also seems to dry more quickly than other paints.Scott