Painting has a reputation for being difficult, and it is in a way the most important work you do. No matter how nicely you have welded, it is the paint that is visible!
So I read a lot online and eventually have some practical experience that I thought I would share.
When it comes to paint, I have come to the conclusion that only the best is good enough. Professional paints are expensive, but are only a trifle in the total budget. If you spend 100s of hours on a project, why gamble on getting back rust in a few years?
For under-body protection see Fluid Film rust protection
Read about welding here: Welding sheet metal
More on Land Cruiser 40, read here: land-cruiser-40
Table of Contents
Remove old paint
Sanding
To get rid of old paint and filler, I use a Makita SA5040 sanding machine with 80 grit Abranet sanding paper. It’s very fast. I sanded down an entire body on the outside in a short day with minimal paper consumption. Abranet lasts much longer than regular paper, but is far more expensive. And it’s worth it. There are many equally good products, but spend the extra money. Sandblasting would take much longer if you do not have professional equipment, but then with the risk of dents and too much removal of steel. Chemical removal is a bit of a hassle and there is a danger that there will be residues in overlaps etc that can cause the paint to bubble.
I also sand over all new steel with 80 paper before priming to have a good grip for primer.
In addition, I sandblast deep rust, welds and other places I do not get to with a sander.
Sandblasting
There are 3 main types of sandblasters. Point sandblasters that have a small bag or cup for the sand, suction sandblasters that pull the sand up from the sandbag with a hose, and pressure sandblasters. Point sandblasting is fine for small things like rust spots, suction sandblasting is in my experience useless for anything other than the smallest jobs. A pressure sandblaster handles larger jobs such as shafts and frames. But you need a big compressor. For normal work, I use a 600 l / min compressor, but it does not handle continuous blowing. So for big things I use two compressors in parallel, 600l + 200l / min.
I only do sandblasting outside. I put a tarpaulin underneath to be able to collect sand for reuse after filtration through a steel mosquito net.
When using a pressure sandblaster, it is important to:
- Use fine sand, the course has a tendency to block the valve in the bottom. I use Red Garnet.
- The ball valve at the bottom is worn over time. Buy a new quality ball valve when necessary.
- Keep the sand dry. Preferably dehumidifies where sand and blaster are stored.
- Use 2 water separators. One on compressor, one on blaster.
Paint
Of the paint products, I swear by 2K, two-component products. These are much stronger than the 1K that you get on spray cans. You can get 2K on special spray cans, but it is expensive. And I only use professional paints, normally PPG. It costs a bit but again – a drop in the ocean. You can find it reletively cheap on the internet. Whatever the brand, choose a professional paint.
For primer I use PPG D834 Epoxy. No primer is completely dense, but epoxy is by far the best. To rust, oxygen is needed from the air, so it is important to shut the air out. I have experience with 10 year old repairs. No new rust.
I apply the paint with the low end spray guns from Devilbliss. I also have some of the cheaper ones and they are good enough. Preferably use HVLP guns. These give good results and use less air so there is not so much spray mist. I have 3 different, 1.3 mm nozzle for epoxy and top coat, a 1.8 mm for sanding primer and clearcoat, and a mini gun with 1mm nozzle for small things.
As a topcoat I used on a vintage car 2K polyurethane paint, Delfleet from PPG. It is a single stage paint (no clear coat on top) that is used for trucks etc. It has a relatively low gloss, which I think suites an old used car. For other projects the standard solution, base with clear coat on top.
Most such products should be laid wet-on-wet. That is, the subsequent layer is applied directly after the layer below has been drying a short time (ca 10 minutes flash-off). Check data sheets!
Epoxy
Epoxy has the advantage that it provides good adhesion for paint and filler, provided that you do it within 5 days. This is the so-called Epoxy window. The epoxy only provides an adhesion for about 5 days. Check the manufacturer’s data sheet as this may vary. If you wait longer, you have to sand it. Use a gray sanding mat. (Scotchbrite) There are many opinions about filler straight on steel or filler over primer. I swear to prime first to insulate the steel from air. Filler attracts water and if you have some porosity, it can lead to rust.
I have also tried products that can be applied directly to rust, so-called rust converters. Rust came back after a year. The problem with these is that they are not dense enough. Another thing is that they only work on very thin layers of rust. In principle, it should be possible to apply epoxy to rust as it will then prevent oxygen from entering. Rust does not continue to develop by itself. But I think maybe the rusty area is so porous that it can form air pockets under the epoxy which in turn will lead to further rust development. Adhesion to rust can be a problem. Interesting if others have opinions on this.
If you are really paranoid, you can use a rust converter after sandblasting in places with deep rust. The sandblasting does not reach the deepest pores. However, I think this is unnecessary since the epoxy will seal this microscopic rust.
Choose Epoxy from a reputable supplier, and only 2-component. I have used PPG D834 for my projects.
Undercarriage
The chassis is the most exposed area on a car, but fortunately it does not have to look fantastic. If you want extra protection there, it may be an idea to try a special Epoxy type, Epoxy Mastic. It is used for offshore installations and bridges. It can be applied thickly and becomes rock hard. Personally, I have not tried it, but see several recommend it. There is also Epoxy with added zinc for the ultimate in corrosion protection.
Bedliner
Bedliner, eg Raptor is the new wonder paint for undercarriage. Supposedly used on armored cars as reinforcement. It is a polyurethane paint that is applied thickly and that stays elastic. Epoxy is used as a primer. The paint can be delivered with RAL colors..
Filler / Bondo
I use polyester filler, a fine for small things and a medium for larger things. For sanding filler, see below.
Over the filler I apply a new layer of Epoxy to insulate the filler and cover where I have sanded down to steel. If you have done a very good filler and sanding job, you can apply the top coat immediately over the Epoxy after venting for about an hour. Wet-in-wet. It provides the best adhesion for the paint.
But as a rule, it is too time-consuming and tedious to sand the filler so good, and pores in the filler will always occur. So I use to put a so-called sanding primer (2K it also) over the filler/epoxy, and then sand lightly with fine paper before the top coat.
Sanding
When sanding filler, be careful not to use too coarse paper. It gives deep scratches that will be difficult to sand away without making pits in the filler. You can use 80 first to take the biggest drafts, but go over to 120 and 240 as quickly as possible. Finish with a round of 320.
For large surfaces, I use a long sanding block to avoid local depressions, and I only hand sand. It is very difficult to get good results with a sander.
Grits, rule of thumb:
Filler (and first primer) on top of 80
primer on top of 180
paint on top of 320/400
For large surfaces, I use a long sanding block to avoid getting local depressions, and I only hand sand. It is very difficult to get good results with a grinder
Welding primer
If you weld yourself, problem areas will arise. There may be cavities that you do not get to paint, or places with overlaps that are spot welded. Here it is advisable to use welding primer. This is a primer that contains metallic zinc. When heated, the zinc separates and galvanizes the steel. Paint as much as possible with epoxy, except 1-2 cm from where it is to be welded. Here you apply welding primer just before welding. The cavities must of course be sprayed with an additional cavity protection. I use Fluid Film for this.
Spraying technique
One of the things you fear most when painting is running. So as a beginner, I started with the underside of the car to practice. The epoxy is very easy to shoot. I have never experienced any running with epoxy The top coat, on the other hand, ran a lot, especially around protruding details and in corners. Such places must be taken with patience. Start with the difficult places, give them a coat from one angle, go somewhere else and work and then come back to shoot from another angle. If you try to get coverage in an operation, it is guaranteed to run.
When I started inside the car, I was overly careful. On the dash I used too little paint, and then you get orange peel. It was just sand down and try again. This time I found a test piece and experimented with the amount of paint until I found the point where there was enough paint to give a smooth surface, but not so much that it ran.
I have painted the inside in two coats. First the floor and front, then wheel arches and side walls at the back. It presents a new challenge where old and new paints meet. When this happens in a corner it is relatively easy, it is worse on flat surfaces. My first attempt was unsuccessful. Then I just sprayed into the old area for a while and hoped for the best. (Masking tape is not a good idea. It gives ugly stripes.) But due to low saturation of the paint in the transition area, it became an area with a very rough surface. Just to sand down and try again.
The trick is: you spray a bit over the old paint. Then you take some of the paint, dilute it with 50% of the thinner you use for the paint, and spray the transition area plus a little further into the old paint. If you want it to be perfect, you should spray once more with clean thinner on top, but this is supposed to be extremely difficult. The risk of old paint starting to bubble / loosen is very high. So I dropped it.
The result is a slight dullness in the transition that you can see in oblique light, but can barely feel. It can be rubbed down when the paint has hardened.
Seam Sealer
Use seam sealer in all plate joints. As is well known, this is where the rust begins. I use 3M 08694 1-component polyurethane seam sealer. I apply it after the first epoxy primer. Seam sealer can be overpainted after one hour. It is claimed that bitumen products like Sicaflex / Tec7 can be used, but it must harden for 6 days before it can be painted. There are also 2K seam sealers that dry faster.
Fix defects
If you see that it starts to run somewhere, it is possible to save the situation if you are fast enough. Wipe off the paint from the area where it is flowing and immediately spray on new paint. But it is too late when the paint has started to dry.
No matter how good you are at painting, you sometimes get runs. You can then sand down and repaint. But it’s not funny if it’s the top coat. If you sand then you will definitely sand yourself down on the primer around the run itself. Luckily I found a trick for this on youtube that I have tried successfully.
Use filler over the run and a bit of the surrounding area. Then sand with a relatively coarse paper until most of the run is gone. The filler will protect the paint around the run itself. Then continue with finer paper, and finally 1000 or 1500. Any small filler residues can be removed with a solvent (thinner).
Protective equipment
Lakkproduktene som er nevnt her er svært giftige, og verneutstyr er absolutt nødvendig. Helst bør en ha friskluftmaske, men aktiv kullfilter maske fungerer også, men betinger da veldig god lufting. Jeg bruker en 3M 06941 maske. De koster ca 400 kr stk og varer lenge hvis du pakker de ned i den lufttette posen etter bruk. De kan og bestilles fra Tyskland (samme som over) for ca halve prisen.
Engangshansker er også en selvfølge. Produktene inneholder cyanater, som navnet indikerer ganske giftige greier som tas opp gjennom huden.
The paint products mentioned here are very toxic, and protective equipment is absolutely necessary. Ideally, one should have a fresh air mask, but an active carbon filter mask also works, but then requires very good ventilation of the room. I use a 3M 06941 mask. They last a long time if you pack them in the airtight bag after use.
Disposable gloves are also important of course. The products contain cyanates, and as the name indicates quite toxic things that are absorbed through the skin.
I made a fresh air mask based on a used full face mask, a used hose for a central vacuum cleaner and a ventilation fan. It works very well, except that I don’t see good enough. In next version I changed to using a half mask instead. The mask itself is a dust mask with some modifications. The two pipes on the side that contribute to the alien look are to avoid drawing air in through the exhalation valves. When you inhale, it takes parts of a second before the exhalation valves close. Enough to pull in some paint dust. With the pipes, you rather draw in some of the old exhaled air.
I use the fresh air mask if I have to paint a few small things in the winter. The bigger things I take in the garage in the summer. Then I hang tarpaulins on 3 sides of the car, use the 3M mask and paint with the garage door open for ventilation. It’s working surprisingly well. I can only remember once I got a fly in the paint.
Disclaimer
This blog is not commercial and the only reason I mention product names here is because I have personal experience with them. There are many products with similar quality. Maybe except for 3M then. If 3M has a product I need, I buy it.
