Rust converter (like rust mort)

[bunkhouse]

Prime it with zinc-rich primer.

[AydinZ71]

Ok I can help with this. I restored my race car from bare metal over the past three years and learned a lot about paint (did all the work myself), rust, and metalwork. Here are some facts for you.

 

1) nothing, and I mean nothing, is more critical than adhesion. If you don’t want pieces to chip off when they get struck, you have to focus on adhesion which unfortunately, means attention to detail. 
 

2) no coating will stick better on steel than to an 80-grit (ideally with a DA (dual action) sander) sanded surface. The surface than needs to be wiped with oil/grease remover (very important) prior to applying coating.

 

3) second-best option for surface prep is an acid wash. Stick to phosphorous acid, as other kinds tend to be too harsh and make adhesion more difficult unless it’s been 100% diluted and removed. 
 

4) remove all rust with a wire wheel until it’s shiny, then scuff with 80-grit. Do not rely on acid to “eat” rust unless it’s literally just surface rust. You will tell if you wet a paper towel with phospho acid and it wipes entirely off. That’s surface rust. Anything deeper needs to be removed mechanically. 

 

5) if removing surface rust with acid, you must while-down the surface with water and a rag multiple times (ideally distilled water) until nothing else domes off. That powdery residue surface you may see is bad. That will get in between your coating and the steel, and prevent adhesion like powdered sugar.

 

6) read the TDS of your coating. Unless it explicitly says “direct to metal, DTM”, you must apply a quality epoxy over your bare metal first, then spray your urethane over the slowly curing epoxy. DONT wait too long, read the TDS. You don’t want to have to sand the epoxy… very time consuming.

 

unfortunately, if you want a factory-like long-lasting finish, attention to detail is critical.

 

I find rustmort to be too aggressive for me. It will eat your concrete immediately if you spill a few drops (you can see it bubbling). I prefer industrial metal descaler. You can find this at any industrial metal supply shop.