Quickly and effectively prepping carbon steel for paint

[Franknstein]

Hi all

I've been welding up a boat trailer for a couple months part time, and I'm about ready to start painting. However I am looking for the quickest, least time consuming method of stripping the oxide coating (see pic 3) off the steel and some paint in areas... I have been using flat sanding discs on a 115mm grinder, but find they clog quickly when it gets to the parts of the steel tubes with heavy black oxide, and also I have to keep angling the grinder... seems that perhaps I might be using the wrong attachement?

I've tried a wire brush on the grinder (not the twisted type though), are the twisted any better? The normal wire brush is useless.

I've sandblasted in the difficult areas and at all the welds, so its just really the flat long sections - my sandblasting rig is just not up to the whole job, nevermind finding a place to do it....

Please can someone suggest a good method... the prep of this is very important as I will be painting in cold zinc paint, and then 2k, as the trailer will be dipped in salt water.

Pics...

 

[Country Joe]

Hi there, and welcome to the Forum!
That looks like millscale, that nasty blackish coating. (oxides on steel are usually of a rust colour, strangely!) I usually find a flap disc gets rid of it quickly and easily.
If you're using a flat sanding disc, then I'd not expect it to last too long, but flap discs are like chunky, interleaved sanding sheets (possibly with some other kind of abrasive in them, too), last quite a while without clogging, and should zip through that with no problems.

All the Best,
CJ

 

[langy]

Flap wheels just skate over it, it will get it off eventually, whereas a poly disc will remove it very quickly and leave you with bright steel

 

[Franknstein]

Cool. Thanks for the replies. Excuse my ignorance... But what does a poly disc look like?

 

[bigbadbugga]

http://www.weldequip.com/cleaning-fleece-115mm.htm

 

[langy]

Cool. Thanks for the replies. Excuse my ignorance... But what does a poly disc look like?

Here ya go. I always use them to clean before welding as they give a nice clean surface.

 

[the snooper]

are you fitting any keel rollers to the trailer ?

 

[Franknstein]

Thanks.
Yes. I've already ordered the keel rollers... They were delayed though... that's pretty much all that's left to weld now.

 

[Franknstein]

For anyone interested, heres a quick recap of the project so far - lots of pics below...

Anyone ever towed something with an axle width of 2060mm or wider? I increased the axle width of the original trailer from 1800mm to 2060mm, and am concerned about towing on narrow road with oncoming traffic...

 

[the snooper]

a transit including door mirrors is 2360 mm so i would imagine with out mirrors it would be a similar width to your trailer your trailer maybe even less, so i cant see any problems there

 

[the snooper]

im not a fan of those types of trailer i prefare all rollers, if the boat rests quite hard on the timber the only easy way to remove the boat is to float it off, and winching back on is more difficult,
nice job on the trailer though

 

[Franknstein]

Yes, I know what you mean, just depends on the angle of the ramp though... I will be carpeting the bunks, and was advised to apply furniture polish to the carpeting to reduce the friction... glad you like the work... its certainly taken a lot of time, far more time than I anticipated... my other half wants to leave me now cos I'm never at home

 

[the snooper]

yes had that argument especially on a hot sunny day, out in the boat forget work.
i think you would be better to get a silicone lubricant spray for carpet or a wax,
i parted with my boat some time ago now sunny hot days make me wish i hadnt

 

[Franknstein]

i parted with my boat some time ago now sunny hot days make me wish i hadnt

Well those sunny days seem hard to come by recently - makes me wonder why I ever bought it... but hopefully will all be worth the blood, sweat and tears in the end. What boat did you have?

 

[bryon4000]

Wow! What a great job on the trailer. That is really impressive.

I realize I'm replying quite late to this thread but I had the exact same question as the original and this thread answered it for me - thanks guys. I found a you tube video showing the performance of this type of disc - just what I need

http://www.youtube.com/watch?v=C6ZgC5XER_o

 

[Keith 66]

Curious as to why you are painting it? galvanising is far superior & after you cost in the discs, prep time then add the cost of the paint on it seems counter productive.
I just did a bunch of launching trollies & it was no more expensive having them hot dipped.