Rust Repair tips n tricks

[Metalhead96]

Hey all

I'm about ready to start making my patch panels for the piazza and thought id start a thread relating to how every goes about fixing/treating/removing rust

Couple questions to start this off

- what's the preference for replacing steel? Do I go get a fresh sheet (1.2mm thick) and start there? Reason I ask is I have some panels laying around from other cars I can use bit more modern so they would obviously be treated differently when manufactured. 

-what's the better products to use for treating/sealing rust? Brush on vs spray? 

-best order to do things in? Example: cut patch, rust treat area, weld through prime, weld patch, paint? 

Chairs and tables

[Spencer]

Get some cold rolled steel not zinc plated, its easier to work with. 1.2mm is too thick get 0.8 or whatever the correct gauge is.

To keep it simple go get some 2 part epoxy primer you can brush it on or spray. Use it for everything to do with covering up exposed steel you dont need any other products.

Many ways to skin a cat but I ended up with a process like: make a patch -> paint shit with epoxy (back of patch, inside crevice, seams etc) -> let it cure overnight -> weld it in -> epoxy everything and done. If you epoxy between spot welded seems you need to use like a spot weld or flat drill to clean it off before welding, its not "weld through" but it sticks like fuck even close to weld areas if its cured.

Rust treatment products are also mostly bullshit, you should aim mostly to remove with abraision. The legit products are acid (usually phosphoric) works to remove rust but mostly on big flat panels or parts you can remove and soak, inside crevices its not as easy to use as it goes places you dont want it and cant wash it out.

Also if you are mig welding stick it in with basically big tack/spot welds and grind them down as you go (like do them 2cm apart then clean it up/repeat), its slow as fuck but give the best results less warp etc. If you dail in this method you get almost invisible weld seams, practive first make sure your spots penetrate enough not just weld on top. Sometimes some panel beating on the way helps to flatten things out.

[Bling]

I used to do batch work, so would cut a bunch of rust out, then spend the time making all the panels to replace it. Then paint as above. Saved getting all the tools out each time I was doing the next repair. I don't have the space to spray so I used to just make up a mixing pot of epoxy primer and brush it over all the repairs. Bad memory meant I had a list of repair locations written down , so whenever I had some primer mixed up i'd give them all their next coat. Areas inside often got 3-4 coats as if I mixed up too much primer.

[Metalhead96]

1 hour ago, Spencer said:

Get some cold rolled steel not zinc plated, its easier to work with. 1.2mm is too thick get 0.8 or whatever the correct gauge is.

I measure a piece I cut out and it was 1.2mm thick, would it be okay using something slightly thinner or does it not matter too much and is just easier to work with. 

Also cheers for the feedback man, will definitely change up my plan a bit

[Metalhead96]

@Bling yeah I'm the same and keep forgetting how many spots I've got to do. Will most likely go in stages like you say, all the areas I've got to replace steel have been cut out so far and will spend a weekend treating and cutting out patches etc

[Metalhead96]

Also what about areas that have more or less bubbled up but not rotten through? Clean it back as much as possibly and epoxy primer? 

[Adoom]

6 minutes ago, Metalhead96 said:

I measure a piece I cut out and it was 1.2mm thick, would it be okay using something slightly thinner or does it not matter too much and is just easier to work with. 

Also cheers for the feedback man, will definitely change up my plan a bit

Use the same thickness as what you are removing, makes the welding easier. 

Watch all of Fitzee's Fabrications on youtube. ....But he does like to use thicker steel so he doesn't have to worry about making it too thin when grinding back welds.

[Bling]

Would probably need an example. But often things bubbling up, started corroding on the other side of the panel. If it's 100% just on the front side of a panel, then what i've done is wirewheel, then metal prep with an acid product to get in the pits, then clean, clean, clean, then epoxy prime. 

[Spencer]

Bubbling up usually means cut it out. Acid washing is for like surface rust or pitting that you want minty clean before paint and you cannot smash it with abrasion.

If your car is 1.2mm then thats fine buy that, find it strange though not many cars actually have thick metal on them. Most old US cars etc have had under 1mm steel. I say get the thinner shit as its easier to form, same reason for getting cold rolled its amazing to work with after fucking with zinc sheet which is junk. I would have both thicknesses on deck if you can get it easy.

 

[Spencer]

Small air grinder or electric equivalent grinder with smaller diamiter cutoff wheels used on the edge for grinding welds down. Again slower but you can get it near perfect then finish with rubber backed sanding disc on grinder. Dont use grinding or flap disc IMO.

[xsspeed]

@Spencer what was that brand of epoxy primer, came in minty green colour

[xsspeed]

also pls cover epoxy prime, vs etch prime and use of bog

asking for a friend / @Indiana_Jones who i helpfully told to read the entire paint thread

[Indiana_Jones]

7 minutes ago, xsspeed said:

also pls cover epoxy prime, vs etch prime and use of bog

asking for a friend / @Indiana_Jones who i helpfully told to read the entire paint thread

What a good friend you are. 

My learning so far from that thread and other internet places is that etch primer does not go on or over filler. 

[Bling]

https://www.autorepairsdirect.com.au/blog/differences-between-epoxy-primer-and-self-etch-primer-for-bare-metal

Pretty sure this threads consensus is epoxy primer the world.

[Spencer]

15 hours ago, xsspeed said:

@Spencer what was that brand of epoxy primer, came in minty green colour

Yeah the cheapest/best one is generally protec epotec 408. It was their commercial product so cheaper but super legit. Its PPG epotec 408 now they got taken over ages ago, I got some recently its about $150 dollarydoos for a 4L kit used to be like $110

 

 

[Spencer]

Etch primer is like a million year old paint technology, for the days of single stage solvent cured paints it was the stuff for metal adhesion. Its gargabe though if you leave it around it will rust, it does not seal and it will fuck out if you put a 2 part product like bog over it (it can peel off etc). I would only use it if I was painting some 1K laquer or something on the cheap, even then why bother you can spray 2k epoxy it is not as deadly as 2k urethane to do at home.

You can bog on metal the data sheet will tell you to do that, however most will do it on top of epoxy primer I think both are acceptable. Then epoxy on top and you good. Buy good filler evercoat etc.

[JustHarry]

Epoxy isnt a a sealer anymore all automotive epoxy are porous . The only one that was used to be the old green galsurit one.

Now because of health a s saftey rules the epoxy as good as they used to be.

6 months is shelf life for a repair in epoxy. longer than that you need to strip it back and recoat.

The best way to seal stuff that's gonna be sitting for more then 6 months is to epoxy then slam a coat of cheap 2k over top 

But also this is just the internet and I'm no expert so do as you please. This is just how we work doing restoration work. 

Edit: buy some keyphos and just keyphos the bare metal till your ready to epoxy all your repairs at the same time and start the paint process . But this also needs to be stripped fully as it's not ideal to paint over 

[Metalhead96]

@JustHarry  should have patches done and painted over within a month at most if all goes to plan. 

What's the go with cavity waxes/tectyl/fish oil etc for spraying inside scuttle panels and chassis rails. One better than the other or do they all do the same job? 

 

[JustHarry]

30 minutes ago, Metalhead96 said:

@JustHarry  should have patches done and painted over within a month at most if all goes to plan. 

What's the go with cavity waxes/tectyl/fish oil etc for spraying inside scuttle panels and chassis rails. One better than the other or do they all do the same job? 

 

Cavity wax is the modern version of fish oil.

Theres not really a bad cavity wax tbh. They all do the same job.

But that's a very last job. Once no more paint needs doing as it can cause problems with fish eyes 

[moparmuppet]

Is cold rolled steel easy to get hold of?  I have only ever used zintec but it hasn't been a hassle and the offcuts aren't rusty years later.