Helpful tips on sanding surface rust

Gonna address some of the surface rust on the Volvo today or tomorrow. Borrowed an air circular sander from work and bought 80, 100, and 150 grip pads. 

Never done this before , any advise or tips?

Thanks

Dan

Keep moving as fast as possible.  You can induce significant warpage into panels by working a spot for too long.  Heat is the enemy.

Does the sander have the vacuum thing built in? If not, you’ll need to use a vac to keep rust particles from binding together and ruining sandpaper sheets so quickly.  (or compressed air if you want those rust particles suspended in the air!)

In reply to Trackmouse :

It does not. Thanks!

Wire wheel not sandpaper for this job. Then a converter or encapsulation treatment.

What NOHOME said.  Rust makes pits, sanding needs to grind the good metal away to get to the pits, wire wheels get the pits without mass metal removal.

An even better way if you are not a wuss is a spray bottle full of Muriatic.  Squirt squirt, wait a couple minutes, rinse off, repeat until rust is a distant memory.  Stay upwind or hold your breath while spraying.

You own a Volvo old enough to be built before Swedish perfection rust prevention, and not some wuss mobile like Ford Explorer or Toyota RAV4, so I am confident you can spray hydrochloric acid at your problems without issue.

In reply to Knurled. :

where would I even buy Muriatic if I chose to go this route? 

dankspeed said:

In reply to Knurled. :

where would I even buy Muriatic if I chose to go this route? 

 

Home Depot or Lowes, about $7-8/ gal. Cleans down to the pores, my preferred method. Water neutralizes acid. Fumes are harsh, stay upwind like said.

https://www.lowes.com/pd/Jasco-1-Gallon-Muriatic-Acid/50298111

https://www.homedepot.com/p/Klean-Strip-1-gal-Green-Muriatic-Acid-GKGM75006/202690263

In reply to fasted58 :

So would I do a 1:1 solution of muriatic and water or straight muriatic? I assume you spray it on and wait then rinse with water. Can I spray with a primer right after rinsing and drying?

In reply to dankspeed :

Straight muriatic.

Dunno where or how bad your rust is. Sand paper any heavy rust. Muriatic will not strip paint but may discolor it, tape off w/ plastic if necessary. I apply muriatic w/ cheap chip brush but spray bottle would work. Rinse w/ water, you will see any rust left, repeat till goners. Use plastic pan to dip brush or catch runoff, muriatic will not hurt plastic.

Bare metal will start to flash rust, sometimes immediately. Scuff w/ purple pad and blow off w/ air then prime.

Not many muriatic fans here but I believe in it, better than thinning the metal by grinding good metal away to get down to the pits. 

edit: practice on some old rusty scrap metal to get the hang of it and see if it's for you.

Soda blaster, but be prepared to need a compressor that churns out 12CFM at 90psi 

Many folks prefer phosphoric acid (rather than muriatic).  It's what I've been putting on things to help kill rust.  I'm lead to believe it is the active ingredient in POR-15's own brand of "prep" stuff.  It's another option for you.

This thread prompted me to do a search about the differences.  Here's an informative thread that talks about both acids and seems to show two viewpoints that can help folks decide when they want to use which.

Other stuff I'm reading suggests that Phosphoric acid works more as a rust converter than remover.  It sounds like miriatic (aka Hydrochloric) acid actually "eats" the rust and then gets to work on the base metal.  Not a bad thing...just as long as you know it and are prepared.

Some photos of what you are working on would help.  If it's truly what I'd call "surface rust" there won't be much loose stuff to knock off.  You can mechanically remove it like you are planning, wipe it down with some phosphoric acid, wait a few minutes, wipe it down with some paint thinner or brake cleaner, and then start painting.    That said...I'm not a paint and bodywork type.  I'm more the nuts and bolts type.  

This guy on an angle grinder will get the rust out of the pits. The oat-cakes are OK for paint, but I dont find that they dig down into the pores.

both muriatic and phosphoric are good ideas. You pretty much need to dump a box of baking soda on the part after the muriatic. The phosphoric actually leaves a coat that wont rust.