facthunter Posted January 30, 2023 Share Posted January 30, 2023 The DC will be derived from AC by being rectified. With 3phase etc this is above my pay scale. I just set as per instructions. Nev 1 Link to comment Share on other sites More sharing options...
onetrack Posted January 30, 2023 Share Posted January 30, 2023 (edited) Quote I remember the old man telling he was working at lakes entrance when big sheets of paint started falling off a trailer nearby. Someone was welding on it with a DC welder. Why would that happen. What happens in a lot of trailer painting jobs, is they don't remove the mill scale, which is caused by the rollers on the red-hot steel plate coming out of the steel mill, forming a coating of hard iron oxides on the plate. The coating protects the steel plate for a while, until moisture gets under it - then it simply falls off! - taking any paint that has been put on it, off with it! The only cure, is to sandblast the trailers before they're primed and painted. Some steel plate is worse for mill scale than others, but all steel plate has mill scale on it, in varying thicknesses. I bought a new Drake 100 tonne 4 rows of 8 widening low loader, with a 4 rows of 8 dolly, in 1993 - and Drake were very particular about sandblasting the whole rig, before priming and painting it. They were also very selective with their steel plate, preferring Japanese steel plate instead of Australian steel plate - because Drake reckoned the rolled finish on the Japanese steel plate, was much better than the Australian steel plate. Lazy and el-cheapo trailer manufacturers won't spend the money and effort to sandblast their trailers, they simply hose them down and paint them. https://en.wikipedia.org/wiki/Mill_scale Edited January 30, 2023 by onetrack 2 Link to comment Share on other sites More sharing options...
facthunter Posted January 30, 2023 Share Posted January 30, 2023 That's true. The mill scale is the oxide formed when its being hot rolled and is itself an oxide and will easily convert to Hydrated iron oxide, The "Usual' Brown one that trendies like to form on their gates.. IF you are serious about your trailer's life have it GALVANISED when made. Some Mini Mokes were done this way. Unfortunately it will anneal the steel but unless it's the modern HIGH Tensile It won't change that much. Nev 1 Link to comment Share on other sites More sharing options...
onetrack Posted January 30, 2023 Share Posted January 30, 2023 (edited) Quote Times have changed. Remember working in Timor 2007/08 watching Aussie Army recovery crew retrieving a Landcruiser been totally submerged in fresh water river for a few days. Winched out and fully operational again two days later. No electronics in that truck… I've seen a couple of old farmers filling a water tank on the back of their 1942 Chev 1 ton truck, with the truck parked out the front of the dam they were drawing water from. As the tank filled, the handbrake let go, and the truck rolled back into the dam and into 12 feet (3.65M) of water! It ended up well and truly submerged. They went home and got a rope and a tractor, and one of them duck-dived on the old Chevy until he hooked the rope on the bumper! They pulled the old Chevy out, drained the cabin, drained all the oils, let the seat air out in the hot sun for 3 or 4 days - then the blew out all the electrics with an air hose on the compressor - and she started right up again! She ran for years and years afterwards as the farm runabout, until the farm was sold, and the truck went to some other owner! The only problems they ever had with that old Chev, was they used to regularly break front springs in the rough paddocks - and that would have been due to a lack of shock absorbers. You could never do that today with the plethora of electrics, electronics, wiring, and poorly-protected harness connectors. The local Maritime museum mob are gurus at recovering items left in the sea for mega-amounts of years. They have specialist chemicals and processes, including electrolysis to recover items lost under massive coatings of rust and scale and marine growth. I spend a lot of time on equipment and machinery restoration, and I seem to spend the bulk of my time fighting corrosion. I use a citric acid bath, and then a high-pressure cleaner wash, and then a spray of phosphoric acid solution (about 5% - 10%) to prevent flash rusting again. It's the simplest, cheapest, safest, and most effective way of recovering rusty items. The amine solutions such as Corrodip and Evapo-Rust work well, but they're expensive, and you still need to pressure-wash and spray with phosphoric acid solution afterwards. Another good product is Exit-Rust, this utilises Iron tannate from Poplar bark. The tannins in bark in many trees are very protective on metal. I've noticed the nuts from the Qld Box trees we have here as street trees are full of Iron tannate, they leave the typical blue-black coating of tannin on the steel ute trays after a rain. These Iron tannates are the reason they can pull almost rust-free sunken WW2 Russian and German tanks out of bogs and swamps in Europe after 60 or 70 years - all these bogs and swamps are full of Iron tannates, as the bogs and swamps are surrounded by Poplars. However the Iron tannate coating doesn't last when exposed to the weather, it must be protected. Edited January 30, 2023 by onetrack 2 Link to comment Share on other sites More sharing options...
turboplanner Posted January 30, 2023 Share Posted January 30, 2023 12 hours ago, fallowdeer said: Times have changed. Remember working in Timor 2007/08 watching Aussie Army recovery crew retrieving a Landcruiser been totally submerged in fresh water river for a few days. Winched out and fully operational again two days later. No electronics in that truck… I went to an Army briefing in Townsville where they were calling tenders for new Ground Equipment which they use today. They said they'd finally had to scrap all the landrovers landed by driving in the sea at Timor, so one of the conditons was new vehicles have to be sea water resistant to allow barge landings. Link to comment Share on other sites More sharing options...
facthunter Posted January 30, 2023 Share Posted January 30, 2023 In the early stuff most parts were cast iron and steel, even gearbox cases and bell housings. With aluminium alloys with zinc and magnesium corrosion is much more rapid. Look at the fancy coolants used. Nev 1 Link to comment Share on other sites More sharing options...
onetrack Posted January 31, 2023 Share Posted January 31, 2023 The earlier Landrovers were shockers for chassis corrosion, too many pockets inside the box-section chassis without adequate drain holes, that retained salt water and salty mud. Their chassis was built using small sections welded together - unlike American and Japanese vehicles where the chassis rails were pressed from much longer lengths, and drain holes were punched in as part of the pressing process. Link to comment Share on other sites More sharing options...
facthunter Posted January 31, 2023 Share Posted January 31, 2023 They all rust when sheets overlap. In aircraft riveted laps (unless bonded as well.). Cill Panels and above headlights bottom corners of mudguards. Anywhere foam rubber etc is used Air conditioner plenum chamber. Air exit venting aft of rear doors. and of course where FIDO pee's in the back of the ute. Nev 1 Link to comment Share on other sites More sharing options...
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