Planning for rust when fabricating?

[YotaAtieToo]

I was spoiled with virtually no rust where i learned to build things. Now I live in somewhere that they use deicer during the winter. Luckily it's no where near the rust belt, but still a factor.

I built this bumper for my 4runner about 4 years ago before we moved and it's got more rust than I'd like. I plan to sand blast it, and either repaint or powder coat. But now looking at it, there are places I can see holding water/deicer.

This one I can just drill a hole to let stuff drain

Would it be better to cap this after sand blasting? Or leave it open and just blast a ton of paint in?

This was a support rib on the front panel, no idea what to do with it. I don't want holes on the front side as they would be pretty ugly and maybe not even help that much. No idea what to do to help there.

I'm sure the rust belt guys are laughing at this stuff, guess I should have just bent some channel iron around the front

Figured this could be a general tech thread with tips to prevent/mitigate rust also.

 

[HYDRODYNAMIC]

Same concepts as sanitary food equipment fab. If you search around you can find literature covering every aspect of it. Instead of bacteria its rust growing in the same areas.

Some of the concepts are:
Everything at an angle so nothing can sit on a flat surface or collect.
No open cavities, seal everything, minimize tube and use channel, angle, and bar when possible. Cavities can hide water rusting from the inside out.
Don't have any clamped surfaces unless they are sealed. For non food, you can use adhesive to seal out moisture when bolting parts together. 3M tape, glue, silicone.
Welds need to be contiguous and smooth. Rough welds and starts and stops are all spots for water to hang onto and weep in.

Some of the worst builds for this are desert go fast. Dimple dies, axle trusses, shock mounts, sub frames.

 

[Slander]

I try to keep holes to a minimum, like hydro said no dimple dies and speed holes. I also use some high zinc primer from duplicolor and it kicks ass. Sucks if you have to repair it if you don't get it all off and weld over it, but it works! Leaving brackets open on the bottom helps as well.

 

[NDCjeepsmith]

On trusses and the like I've started painting with steelit before welding on. That way the majority is covered inside.

You could do the same with some of those spots you're considering capping.

 

[YotaAtieToo]

On trusses and the like I've started painting with steelit before welding on. That way the majority is covered inside.

You could do the same with some of those spots you're considering capping.

I was wondering something like that.

I could also cut the bottom section out, would be a bit of a pain, but not impossible.

 

[arse_sidewards]

I was spoiled with virtually no rust where i learned to build things.

I'm pretty sure you went off on some "hurr durr norcal isn't a desert shithole" rant last time someone mentioned this topic. Said rant seems to have aged well.

But now looking at it, there are places I can see holding water/deicer.

When people from places with an actual climate say that people like you pick up all sorts of shit habits when it comes to fabricating shit to actually last this is exactly what we're talking about.

You should've thought about all that shit in the initial design. Yeah you can drill holes but it's gonna rust around the holes. You need a clear path for stuff, dirt and debris as well as moisture to get out.

At a minimum you should've clipped the inside corner of all your gussets to make a drainage path but why would you plan ahead like that when being dumb has worked so far.

At the end of the day the only permanent solution it to pack up your carpetbagging ass and return to California.

 

[LowDown]

My son and I recently built a goose neck hitch for his K20 that we didn't want to rot from the inside out. We made sure any open cavity had at least one chamfered drain hole and an opening to fit the garden hose in to flush.

Check out Rustoleum 9100 series epoxy mastic based paint. In my 5 years of using it, it's held up really well to East Coast brine / road salt / de-icer, etc. I've got it on everything; - FJ wheeling truck frame, axles, and cage, my DD 3500 frame (that I take out on NC beaches multiple times per year) open car trailer, and my son's K20. It's become my go-to coating.