Get it.
Clean it.
Strip it.
Paint it.
USE IT!

I repaired these boxes for use as geocaches, as they are tough as hell, waterproof, fire proof, and can stand up to prolonged periods outside, under water, and under ground.
They are great for caching supplies, protecting equipment or documentation, and are relatively cheap compared with pelicases or otter boxes.

Step 1: Introduction

In this instructable my aim is to show you the preparation and repainting of a rusted ammo box.
I want to use these for geocaches, and hence have not troubled myself too much with the end painting, as these boxes will be placed in the wild and ultimately be stolen (an unfortunate part of caching, but inevitable).

The preparation steps give a great surface for painting, and remove a lot of sanding/brushing time, and can be used on any rusted metal.

Rubber gloves are more or less essential for the "wet" steps of this instructable, as the rust sludge is deeply unpleasant stuff

Anyway, on to it, and Please get in touch if you need clarification/information on any steps.

Step 2: Selecting Your Ammo Boxes and Gathering the Tools

The boxes -
I live in the UK and ammo boxes aren't as plentiful here as I'm led to believe they are in the US, this means I'm forced to buy mine from army surplus stores. The boxes I've found are often rusty, dented, or otherwise abused, and have spent along period outside.
Proper selection of the best starting material will give you the best end product.

My advice is to take your time, carefully examine the bottom and insides of the boxes for holes (water collects here and over time corrodes them through), also make sure the box opens and isn't solidly frozen. Stiffness is fine, and nothing a penetrating lubricant (WD40 et al.) and a hammer can't fix.
Also take some rubber gloves, driving home with rusty hands is no fun.

If holes develop later on, during sanding or brushing, I'll show you how to fix those later.

Other tools -
- rubber gloves
- wire brush
- sand paper (any grit will do, bigger the better, and it's a good opportunity to use up old/used paper)
- bar clamp
- plastic tub/trough large enough to hold the ammo box
- paint brushes
- wooden skewers
- painting stand
- newspaper/dust sheet
- brush
- knife/scraper

Chemicals and paints -
- 4+ litres of vinegar
- 2 litres of water
- metal primer
- desired top coat

Step 3: The Vinegar Bath

This is an optional but recommended step, as the contact with the acid in the vinegar loosens, and dissolves, some of the rust and paint already on the box. This makes the subsequent sanding and brushing considerably easier, and gives a nicer end result, but the price is the smell.
If you wish to skip is sanding and brushing will still work, and give you a good surface for painting.

I used:
-40l plastic tub
- 4l of the cheapest vinegar in the shop
- 2l water

Mix this lot together and submerge the box in it for 48+ hrs, rotating the box daily to soak all areas.
I found a weight helpful to hold the box down, as they tend to float, and a plastic bag over the top to keep the rain off.

After its soak, the box will look cleaner, and now is a good time to scrap any stickers/tape/paper stuck to the box off.
A knife or scraper is helpful here, but the vinegar should make this relatively easy.

.

Step 4: Sanding

After its bath and scrape, it's time for a once over with the sand paper.
Clamping the box with a bar clamp makes this step easier, but holding it is a viable alternative.
The sanding should be easy going, and you should soon be at rust sludge with bare metal showing through underneath.
When this happens rinse the sludge off in the vinegar bath, and move onto the next area.

Once all six sides are done, it's time to rinse and repeat on the closure mechanism and underneath the side flaps.

If you're really lucky, the vinegar will have bubbled the paint and it'll slide straight off.

Step 5: Rinse

The heavy rust and paint will come off with the sandpaper but before we wire brush, I tend to rinse the box off to remove the rust paste and vinegar residue. This stops it flicking on you when you're brushing later, you have been warned.

Once it's clean, either leave to air dry or towel it off.

Also, clean your shower :)

Step 6: Wire Brush

Once it's dry, it's time to brush.
Like the sanding, all six sides and under the lid.
This time pay close attention to the edges, hinges, and handle.
The brush should get what the sandpaper couldn't.

Once it's done, either rinse it again, or brush it free from dust.

Your box should be bare metal or scratched paint, and be in a good state for painting.

Step 7: Patching Holes

If you box doesn't have holes, then this step doesn't apply to you. Move along, nothing to see here...

Small holes are no major problems, and can be easily repaired.
I've tried glassfiber in the past, in the manner of a car body repair, but found it messy and time consuming, and didn't feel it offered anything over the epoxy putty method I'll describe here. Ultimately do whatever you feel most comfortable with, they both work and yield long lasting repairs.

First make sure the repair sites and surrounding metal are rust free, this ensures a good bond and a waterproof fix.
Epoxy putty is available in a number of makes and cure times, select one you're comfortable with, and follow the instructions for mixing etc.
Apply the putty to the inside of the box in a fillet, over lapping the edges of the hole.
Push the putty from the inside, so it pushes out of the hole.
Smooth the putty on the outside, so it overlaps the outside edges. You're trying to make a "rivet" that passes through the hole and bulges out, this help holds the epoxy in place against sheer forces.
Push the putty down gently to ensure it grips the metal on the edges of the blob.
Leave to set.
Sand smooth if desired.

Most epoxies will take metal paint without an issue so no need to rough the surface etc.

Step 8: Undercoating

Not essential if you're using a "one coat" top coat, but I find it helps adhesion, and if I was keeping these boxes, I would consider this an essential step.
Undercoating helps the adhesion of the top layer, and helps prevent chipping and peeling of the paint in the long term.

Metal paint is tough stuff, so make sure to protect your surfaces (paint cloth or newspaper) and wear gloves. The paints also tend to have high volatile solvent contents so please do this in a well ventilated area, outside is the best, as it makes your house stink.

I don't clean my brushes when I'm using metal paint, I use cheap disposable brushes, and bin them when they dry out.
A plastic bag over the brushes between uses keeps them usable for several days, and saves you messing around with white spirit.
If you're a brush cleaner, I admire you.

The boxes are best painted in two stages, best described in the photos above, but for clarification.

1- Opened wide and laid flat allows you to paint the bottom, side surfaces and lid.
2- With a skewer in the hinge, and the lock mechanism hanging inside the box, this allows the lock mechanism, sides and lid to be painted.

The handle can be placed in a position where one side is high, and the high side painted under. By switching the handle position when you change the box position the whole lid and handle can be painted easily.

One coat of undercoat is generally sufficient, but follow the manufactures instructions with regard to recoat time, and allow at least a day between undercoat and top coat.

Step 9: Top Coat

Choose an appropriate metal paint in the colour you desire, and repeat the process of painting.
For the smoothest possible results I advise spray paint, or a roller, but these are more expensive options.

If you choose to brush paint, use two light coats of paint rather than one heavy one, as the paint tends to sag which produces unpleasant looking runs and blobs.
Done carefully, you can achieve a glass smooth finish. However this can be ruined by dust, or rebrushing half dried paint, so less is generally more if you want that level of finish.
As I didn't, I was abit slap happy with the paint, so please excuse my brushwork.

Leave it to dry for a few days and let all the solvent evaporate out before you get too rough with it.
This allows the paint to fully harden, and you have a practically-new-again ammo box.

Step 10: Stencil (if Desired)

As an extra detail, I decided to add a stencil to identify them as game pieces.
For ease, I simply printed out a ready made stencil, cut it using a craft knife and stippled undercoat through it onto the box.
For best results, I used a small disposable paint brush (1/16") and taped all but the last 5mm together. This stiffens the brush and helps prevent the bristles splaying under the stencil. Secure the stencil with tape, and blot away.