Body Rusts

[MasterAK47]

Initially there were some spot rusts, I sanded down to bare metal, applied the anti-rush undercoat, then two coats of anti-rust paint followed with final coat of glossy finishing paint. A year later, the rust came back from inside. When I sanded down, the spot of rust has spread bigger. What did I do wrong? please advice, thank you.

 

[joecash]

once rust sets in its there for good - bit like wrinkles in us oldies

 

[martyz]

To tackle rust you must completely remove it, grind every single black spot out,even if it means holing the panel,the area must be bright unblemished metal,then treat,fill,prime and paint.Or if too far gone,replace the panel.

 

[MasterAK47]

Thanks Martyz, I did, I used the disc grinder to grind to bare metal, primed with the anti-rush undercoat paint as what I have mentioned in my last post, but no luck at all. I have repeated twice in 2 years and now is the third year. Some areas have shown holes.... Could it be the paints I bought was too long on the shelves or the ambient humidity was too high when I primed it?

 

[martyz]

Moisture has got to the bare metal somehow,could well be humidity or defective paints.

 

[MasterAK47]

Hi Martyz, thanks for quick reply, I shall try again on the new rust spots with new paints and see what happens. But, how do I know how old are the paints on the shelves? As for getting rid of humidity, I think I shall apply some heat before I prime the sanded area, do you think will it work?

 

[guydewdney]

use a new grinding disc (soft pad, the ones made of loads of small squares of sandpaper iyswim) as old ones hold rust particles in them.

 

[MasterAK47]

Good tips, I shall use the new grind disc this time and to the results next year, thank you.

 

[Dieselman]

Some areas have shown holes.... Could it be the paints I bought was too long on the shelves or the ambient humidity was too high when I primed it?

Humidity won't help if it's really high, but the issue is that the rust is inside the panel and you are just treating the outside of it.

 

[MasterAK47]

Oh, oh, then, what should I do then?

 

[ivan1983]

I am in the process of sorting a bit of rust, from reading around the process I
have decided to follow is.

1.) Grind back to bare metal.

2.) Apply phosphoric acid

3.) Sand with 40 grit paper (I did this as the phosphoric acid leaves a coating which i was unsure if the primer would adhere to)

4.) Apply several thin coats of Bonda rust primer
1L Bonda Rust Primer

(This is the stage im at now)

5.) Wet and Dry to achieve final surface for top coat.

6.) Top coat then lacquer

Im hoping this will hold up

 

[MasterAK47]

Can I get the Phosphoric acid and the Bonda Rust Primer from the paint shop or where can I get them? Thanks.

 

[l5foye]

I would recommend that, after you have cleaned the panel and treated the rust, you apply a coat of fibreglass resin (not the fibreglass, just the resin).
This will ensure that moisture cannot penetrate.

 

[MasterAK47]

Thank you, l5foye, thank all who have given their valuable opinions. I summarized that to treat the rusted areas, I will do the following: grind down to the bare metal; apply Phosphoric acid; apply fibreglass resin; apply several thin coats of Bonda rust primer until it achieves for the top coat; apply the finishing coat then the lacquer. I shall wait for a while to see if there are more good opinions to adapt to before I shall go ahead with this project, also I have to look for phosphoric acid and the Bonda rust pain.