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Comments and advice welcome.  A certain amount of rude responses are anticipated and will be tolerated if the accompanying advice is good :-)

This is really a single question with a few subcomponents.

Summary:

  • Main question - optimum method for removing underbody surface rust on an olde Toyota van.
    Sandblasting is the preferred method so far.

  • Sandblasting media - danger of using regular sand and reasonableness of use with due care.
    (Issue is silicosis).

  • Underbody access for sandblasting.

I'm in New Zealand.
I have acquired (quite possibly unwisely) an olde Toyota Townace van. 
(Main intended use is helping me deal with 35++ years of accumulation of 'stuff'). 

Rust location - underbody: It has what a rust removal expert says is superficial / surface rust scattered across the lower surface.The NZ warrant of fitness people have "orders from above" and are (I'm told and it very much seems) on a mission to drive such old vehicles off the road. (not physicallY).

The rust expert says the rust should remove OK.
Any non superficial rust can be repaired "properly" but there may be none. (One can hope). 

There is some upper body rust, but not so much as to be wholly daunting.  I intend to let experts do the trickier work, but would like to do what I can "easily enough" myself. 

Sand blasting?: I have been informed by people who may know that sandblasting is the best approach - with mechanical methods either producing smooth rust (power wire brush) or undesirable metal removal (grinder etc).I am relatively expert at overdoing things so would like to avoid making unneeded holes if possible. I have ordered an el-cheapo sand blasting gun which should arrive in the next day or few. (I have an air compressor).   

Media: The obvious sand blasting material is completely shunned and decried "normal everyday sand", due to silicosis issues. I feel that the use of a full hood and external air feed should be adequate for such a relatively small job.
Comments on this feeling are most welcome.


People are charging really silly amounts at retail outlets for more approved materials (garnet, metal powders, glass, ... many more)  I have no idea of the amounts needed. I'll be doing (if it works) under body and some interior floor etc.

Ironsand - iron oxide only: I have access to ironsand which contains substantial iron oxide. I wondered how the magnetic component of iron sand would work - with suitably careful removal of non-magnetic silica. 


Commercial sandblasting not an option: I inquired of people doing commercial sandblasting. I'll try others but the order of cost suggested was beyond all reason (or there is a vast amount I don't know). 

Underbody access: This could be a seperate question if desired.

I have neither pit nor hoist readily available. I could arrange a modest ramp system that allowed easy crawl access (and may even be safe) but the idea of sandblasting vertically in a confined space is unattractive. Even in a pit or on a hoist is not overly attractive.
I am attracted by the possibility of tilting the vehicle at an angle. Details as to how are another subject but safety and lack of damage to the vehicle are part of the target. Doing this would seem to be liable to present a much more easily accessed work surface. Comments on this crazy idea are welcomed.

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    As per your opening line, no, rude comments are not acceptable. Per the question, if you can quantify it, how much rust are you talking about? I mean, is it just minor surface rust you are trying to get under control before it does serious damage? Or is there already serious corrosion? Also, I don't think sand blasting is a great way to go because it can cause more damage than it can removing rust ... unless you're are planning on doing a complete frame off while removing all of the soft parts in the process. Mitigation may be a much better choice, depending on the amount of rust there. Feb 28, 2023 at 10:52
  • @Paulster2 - The rust looks quite bad and is widespread BUT the rust repair expert declared it surface and superficial and said it would probably all be able to be removed by sandblasting. I'm an olde (72) electrical engineer but with a good amount of exposure to mechanical activities across the board. I want o keep the $ cost down as the van was low cost and is mostly going to get used for short range rubbish and metal haulinmg as I tody up my 35 years+ of classic messy mess. (At this location). I don't mind cosmetic damage at all. Its very rough. Feb 28, 2023 at 10:57
  • @Paulster2 I'm a moderator on SE EE. I'm aware of the Code of conduct. I'm also happy for a degree of good natured ribbing that fits inside the allowed scope. Trying to revive an old van like this is a crazy idea :-). Feb 28, 2023 at 11:00
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    It would be worth checking that the under body seal doesn't contain asbestos before you start. Some vehicles of that era did have asbestos in the under body seal.
    – HandyHowie
    Feb 28, 2023 at 11:15
  • @HandyHowie THanks. Good point. I intend to wear a full hood with blown air delivered from some distance away. Asbestosis is unlikely to catch up with me before various other things do :-) - BUT I'll still take due care. Feb 28, 2023 at 11:42

2 Answers 2

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I’m adding a second answer to address frame, suspension and drivetrain. I originally took your “underbody” to mean just sheet metal body parts and addressed only that in my other answer, but you’ve clarified now and you mean everything under the vehicle.

This video shows a professional grade needle scaler in use with an adequate air supply, and it gives you a good idea of its capabilities. Cheap-o needle scalers or those powered by a portable compressor are too slow and wimpy for a large job such as yours.

Once the loose rust is removed, a rust converter or encapsulator followed by rust preventive paint gives good results, even if the finished result is not perfectly smooth.

Here are before and after photos showing some of the frame and suspension.

enter image description here

enter image description here

The bright white stuff on the fasteners and adjusters is so-called “liquid electric tape” that I brushed on to prevent further rust. I didn’t want to leave threaded parts as bare metal and have the threads rust away, but coating them with the black polyurethane paint was not an option because of how tough the paint is. The white stuff comes off quickly and cleanly with a wire brush yet still provides adequate rust protection.

I went through this process on the entire underside, including the frame, suspension, steering and brake parts, differentials and axle tubes, drive shafts and the cast iron parts of the exhaust system. The engine itself didn’t need remediation except for the oil pan, which had sheets of rust coming off.

This was a 2009 Dodge Ram 2500 diesel 4x4. I had been warned in late 2017 at my annual vehicle safety inspection that my truck would be failed for rust within the next couple of years if nothing was done, so I undertook to fix it in July/August of 2018, summer here.

I need a heavy duty truck with a snowplow because I live in a heavy snow area at the end of a long driveway. Commercial snow removal service for my property would be ridiculously expensive. Before I decided to tackle the rust myself, I priced out the cost of a replacement truck by going to a local Dodge dealer and telling them I don’t need a truck anymore and I’m not buying anything here, so make me an offer on my truck, I’m selling it, not trading it in. It was clean, had low mileage, everything worked, and even with all the rust underneath, after a mechanic looked at it they offered me US$28K. (US$1.00 = NZ$1.60 today.)

A new truck similarly equipped was in the range of US$60K, so a replacement would be on the order of US$32K. I prefer to buy new and keep forever. So I had a very strong financial incentive to fix the rust and keep this truck on the road for the full 20 years (minimum!) that I like to keep a vehicle.

Unlike you, I was already set up with everything I needed to do the job, most importantly an extra tall vehicle lift in a garage with a 15 foot ceiling so that I could stand fully upright while I worked and adjust the vehicle height at will for comfort whether working on the bottom of a rear leaf spring or the top of a wheel well. And I already had a powerful stationary air compressor.

But the project took two months! I worked at least 4 hours per day for more than 60 days in a Tyvek bunny suit with eye, hearing and respiratory protection. It was brutal! I swept up and saved all the rust flakes, chunks and dust every day and in the end it came to 33 pounds (15 Kg).

Although the rust converter and paint system worked well, I have not named it and I won’t recommend it because other products have worked as well for me on other vehicles without the myriad problems that I experienced. I’ll explain. This polyurethane coating requires two coats, and timing is critical. The second coat must be applied after the first coat has dried to the touch but while it’s still tacky. If you let it dry fully to a hard surface, the second coat just beads up like water on wax.

Complicating the timing is the fact that this paint cures by reacting with moisture in the air and the curing speed depends on humidity. At very low humidity, you get a couple of hours of till the tacky stage, but in the jungle-like summer humidity where I live, it’s tacky in under 30 minutes and fully cured and no longer amenable to a second coat in under an hour. That also means that your brush gets glommed up with cured paint in an hour or two when it’s humid.

I overcame that by running both heat and air conditioning at the same time, which dropped the humidity down into the mid-20% range and gave me a couple of hours of working time. Each painting day I would start a new section, work two hours on it, then go back to where I started for the second coat and cover everything in the same order for the next two hours. If I failed to finish second-coating anything, I had to scuff-sand it the next day to keep the second coat from beading up.

A new brush was needed every day. Ordinary paint thinner doesn’t work on this paint so you have to buy the manufacturer’s own special thinner, which is very expensive. It’s cheaper to just throw away your brushes and start new every day.

And speaking of thinner and solvents, this stuff is hazardous to one’s health. The solvent includes both aliphatic and aromatic naptha and other nasty ingredients. It’s sold to the general public, but it’s labeled for professional use only. It requires serious respiratory protection to prevent brain and liver damage, so I used carbon VOC filters and a tight fitting silicone rubber respirator mask.

But I must say, it’s been nearly five years and I still have no rust to speak of so I accomplished my goal of extending the life of this vehicle. At the cost of spending a significant fraction of my remaining life on the project! (I’m only a little younger than you.)

Instead of this polyurethane, I recommend Corroseal as a rust converter followed by an oil-based rust preventive paint of your choice such as Rust-Oleum. (I have no connection with these brands, but I have used them.) Corroseal is a water based translucent emulsion that turns rust black and prevents further decay. It dries transparent and acts like a latex primer for the top coat of oil based paint. It’s benign stuff. There are no timing issues on the finish coat. You can apply the Corroseal everywhere at once, then follow up with the oil based paint at any time. Although this system is not glass-hard and may not be as durable as the polyurethane, it has given me good service on another vehicle on the same salty roads.

Now your project: You don’t have a lift or a pit. You could make a safe ramp and use a mechanic’s creeper. Not sure if you have the monster compressor you need for either sandblasting or needle scaling or if you’ll use a smaller portable compressor and pause every time the pressure drops below a usable level; if so, you’ll spend most of your time waiting. The tilting car scenario? You have my best wishes.

Whether sandblasting or needle scaling is your method of choice, you’ll still spend over 200 hours on your back under the van if my experience is any indication. Will the inspectors pass the vehicle after all that or will they find another excuse to fail it?

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  • Thanks fo two superb answers. I'll acceppt this one as it completes the set. Now I have to decide what to do :-). Mar 3, 2023 at 8:25
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It seems to me that you've put the cart before the horse. Based on rumor and innuendo, you think the "NZ warrant of fitness people" are going to reject this vehicle for rust, and you treat that like a death sentence for the vehicle. Is it really? Will the vehicle be seized and crushed or will it simply be rejected and therefore unable to be registered for on-road use until and unless the rust is remediated?

Instead of spending a significant fraction of your remaining years on earth on this project based on rumor, what's the harm in going ahead with a fitness inspection and getting the facts? Then you will know if remediation is needed, and to what extent.

EDIT: The OP subsequently commented that the vehicle had already been officially inspected and failed for rust.

If the rust is indeed "surface and superficial" as the expert claims, it is at worst a cosmetic issue, not a structural / safety issue. Sandblasting is totally unnecessary, excessively labor intensive and hazardous to you and anyone else in the vicinity. There are numerous "rust converters" that chemically react with intact surface rust and stop it from spreading. You can then paint over the converted rust and make everything look pretty.

If there is any flaking, bubbled or loose rust, you only have to remove that. You don't need to get down to bare metal. An air or electric powered needle scaler quickly removes loose flaky rust but does not remove solid metal. I recommend it. You will find numerous videos online showing the operation of a needle scaler. EDIT: Beware the cheap-o grade of needle scalers. They are agonizingly slow. I used a professional model with 19 hardened needles consuming 15 CFM at 90 PSI, powered by a 7.5 HP compressor.

Have a look below at before and after photos from below of the underbody of my Dodge Ram pickup. This portion of my de-rusting project was limited to the sheet metal. (I remediated the frame and suspension later.) The steps included removing loose rust with a needle scaler, brush scrubbing with an alkaline degreaser, rinsing with a pump bottle of water, spraying on an aqueous solution of a rust converter, which turned the rust black, then brush painting with a polyurethane paint that's made for the purpose. Two coats and done.

It's not as pretty as it would be if sandblasted, but who cares? It works. And it certainly passes inspection.

Before

enter image description here

After

enter image description here

If you have questions about frame and suspension rust remediation, I've done that on the same vehicle with good results. That would be a separate question.

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  • Well said. I don't know which rust converter you used, but with what I've used in the past, it is of note to not get it on anything you don't want it on, because it won't come off very easily. This includes skin, ground, whatever. What I used was more like paint. It also pretty much destroyed the paint brushes I used to apply it. I take it what you used is a little less fickle than what I used, so good on yah. End product here looks great. I don't think the answer would have the same effect without the pictures. +1 Feb 28, 2023 at 17:56
  • I have 50++ years of engineering experience. I'm an EE but have been involved with a wide range of activities. I try to get the horses and carts in order and accord rumour suitably weighted value. || I consulted two major reputable WOF organisations. In one case I managed inadvertently to speak to a multibranch QC man. On that basis I took the vehicle for a WOF at QC man's organisation. In my long years I have never had WOF inspectors behave so badly or rudely and they were right up there with the worst customer svc experiences I have had. They tried to send me on my way without full ... Mar 1, 2023 at 9:48
  • ... inspection as they said it was too bad and I should scrap it and get anither one. I insisted on my right to an itemised report and they proceeded to itemise rust fail it on mosy inderbody areas and some upper. The upper are no problem. || BUT the rust professional I mentioned says underbody is not very bad as noted above. || He and two (+?) other people in the industry say the WOF people are under orderes to get old vehicles off the road. (This i 35 years old). It will serve my needs well enough if it gets a WOF. Mar 1, 2023 at 9:52
  • Your technical input was interesting and will probably be useful. I'd not heard of a needler. || My question covered underbody rust so is in scope for frame and suspension. I expect that I'd find anything you said on this to be very valuable. Mar 1, 2023 at 9:54
  • @RussellMcMahon Regrets! If there was any indication in your original post that you had already been failed for rust at official inspection, I wouldn’t have questioned your cartmanship. : ) Regarding the term underbody, we in the U.S. use that term to refer to the sheet metal body under the vehicle, so I limited my answer to that. From your comment, you seem to be also referring to the frame, suspension and perhaps drivetrain so I’ll be making a separate answer on those with photos within the next 24 hrs. I do have info that may be useful.
    – MTA
    Mar 1, 2023 at 14:05

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