Kurust, worth using or not?

  1. Hudders New Member

    Messages:
    11
    Location:
    Poole, Dorset. England
    Hi there guys,

    I have an Alfa Romeo 75 that is a running restoration, I'm working my way around the car bit by bit. It's not going to be a show car or anything like that but I still like to make sure I do my best with every part I work on.

    I've seen some interesting posts on car restorations by people clearly very professional, lots of talk about good prep in removing the rust then applying Epoxy primer before a top coat such as Jotan 87a, but I don't tend to see any mention of Kurust or any other rust treatment and it seems noticeable by it's absence, I realise if its painted right away the Epoxy primer should take care of any flash rusting but what if there is a bit of time between that happening?

    I have a bottle and am happy to put it on but not if I'm actually doing more harm than good.

    I suppose what I'm trying to say is, are there any disadvantages to applying Kurust first, will it affect how well the primer attaches? is it just snake oil?

    I'm looking forward to hearing your thoughts on this.
     
  2. bricol Member

    Messages:
    957
    N.Yorks, UK
    Such stuff may slow down rust reappearing, but the only way to remove rust is to cut it out, blast if off, or dunk it in some decent de-rusting solution.
     
  3. earthman Member

    Messages:
    1,261
    That's what a car restoration/body shop guy told me years ago, I doubt that any of these 'brush on/kill rust' products actually last the test of time.
     
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  4. brightspark

    brightspark Member

    Messages:
    28,884
    Location:
    yarm
    curust only stops oxygen getting to the metal . its crap:vsad:
     
  5. Hudders New Member

    Messages:
    11
    Location:
    Poole, Dorset. England
    Yep, I'm with you there, and I will be cutting the rust out where I can, but I'm still learning when it comes to body work, this car will allow me to learn the craft.
    I've just removed the spoiler on the boot lid and the mounting holes have rust around the edges, I've wire wheeled the rust off, its a bit pitted but its back to metal, so in this instance would Kurust be worth adding or do you think it does nothing.

    What about if I've cut out a rusty section and welded a nice new piece in?
     
  6. bricol Member

    Messages:
    957
    N.Yorks, UK
    Before you do anything - go back to the bit you wire-wheeled and drag something hard across it, digging into the new shiny surface. I wouldn't be at all surprised if you see orange rust again. Wire wheels seems to remove the surface dusty rust and then polish the rest so you think the rust has gone.

    Attack it with a flap wheel or a sand blaster, even an Aldi spot blaster, to get better job. A spot blaster would be ideal for rust around mounting holes for instance.

    I had a 75 T/S back in 1993 ish - my mum still mentions it. don't think she was keen on the integrales that replaced it :)
     
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  7. RonA

    RonA specialist in repairing sealed for life equipment

    Messages:
    1,500
    Location:
    Stockton on Tees, UK
    My brother who worked on commercial transport used Phosphoric acid on rusty buses but it was in a much higher concentration than you find in the likes of Kurust
    RonA
     
  8. pedrobedro

    pedrobedro Man at Matalan

    Messages:
    10,242
    Location:
    CX Derbyshire
    Kurust was sold as a rust converter years ago, I haven't looked at it lately is it now a rust remover ? It used to turn red oxidised rust into something black.
     
  9. stuvy

    stuvy Member

    Iv used most of the rust converters over the years on various cars and in places Iv worked

    only thing is Iv never dealt with a car more than once as I mostly do restorations and rebuilds not ongoing maintenance
     
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  10. Matchless

    Matchless Member

    Messages:
    712
    Location:
    Essex UK
    even when you blast a rusty part the rust is still deep into the metal, I think it is a good idea to kill that rust somehow, and drown the whole assembly in waxoil etc. when finished welding / painting,
     
  11. Munkul Member

    Messages:
    1,601
    Cumbria, UK
    There's a big difference in approach.

    1. remove all rust (cut it out, grind it back, etc) to clean metal. apply coatings to stop oxygen/water getting back down to metal.

    2. apply kurust/phosporic acid to rusty metal, it converts iron oxide III into ferric tannates and phosphates, which are more stable than plain rust.... but has limited effectiveness, since even a thin layer of ferric compounds can hold moisture and isn't as good an oxygen barrier as a proper paint coating, etc.

    Anything on top of existing rust layers allows the remaining moisture/oxygen to react and continue corrosion, and if it then perforates the coating (usually does) then you're back to square 1.
     
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  12. Dcal

    Dcal Forum Supporter

    Messages:
    1,820
    Location:
    Antrim Northern Ireland
    I fully concur with @bricol

    I think the 87A has been discontinued and it's now 90A (it's something to do with the solids content) it's pretty much the same stuff just even thicker.
    I like the jotun but other epoxies are available.
    The main problem with epoxy mastics is the amount you need to buy (5 or 10 litres) and how thick it is.
    If you have even a small compressor a spot blaster will make a great job of rust spots.
    After you have blasted them mix just a small amount of the epoxy and apply it with a paint brush. It can then be left untill you are ready to prep and paint.
    Here the thickness of an epoxy mastic becomes an advantage as it will act as a primer filler and it does sand nicely once dry.
    Another tip is get yourself a set of small cheap digital jewelers scales and some plastic cups and mix the epoxy by weight.
    There is a table available for the mixing ratios by weight. I can post a link later if you want.

    I only really use epoxy mastic for suspension and other bits not seen or that will be stone chipped or on really pitted steel.
    So I would touch up the rust spots with 87 / 90a rub level with the surrounding paint then prime the whole area with standard epoxy primer.
    You could use a mastic but it's just more work.

    I'm also a fan of citric acid, if you can immerse parts, as it also leaves a lovely grippy finish that is perfect for paint.
     
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  13. Hudders New Member

    Messages:
    11
    Location:
    Poole, Dorset. England
    Hi Dcal,

    I'm going to get a spot blaster, I do have a compressor, never been sure what media should I use?

    After reading your post about your rebuild of your 75 and other threads here I felt that the jotun 87a was the one to go for, just wasn't sure if I go for the winter grade and have the shorter drying times or go for the standard. I wasn't aware it was discontinued, its on their website and I found a supplier that sounds ok, https://www.rawlinspaints.com/home/...l-paints/1382-jotun-jotamastic-87-alu-wg.html They do do the 90 in alu winter grade but large 20l cans, what do you think I should go for?
    Regarding the plastic cups, I was going to ask about that, so I take it you measure the correct amount of epoxy and hardener into a pot and mix it up, then you have a limited time to apply it before it goes off, and the winter one goes off twice as fast so you cant hang about, what cups do you use then, I assume you use something very cheep as you must go through quite a few. do you save up all the paint jobs to one day or do them as you find them, thats what I would prefer but I'm going to be mixing up very small batches every time.

    Yes Please on the table if it's not to much trouble.
     
  14. Dcal

    Dcal Forum Supporter

    Messages:
    1,820
    Location:
    Antrim Northern Ireland
    Pretty much any media will do for the spot blaster.
    I use j-blast supafine (copper slag) but you could use crushed glass or garnet or aluminum oxide etc.
    Don't use sand because of the health risks and do wear the proper PPE which must include a decent mask.
    There isn't much dust with a spot blaster but there is some so please don't take chances.

    If you can get 87A go for it, 90A is available in smaller tins but the 87 is great for your application.

    I just use winter grade hardener.
    The pot life is plenty long enough for our summers and the lower mix ratio of paint to hardener helps with mixing very small batches.
    Give the paint a good mixing before you decant in to the cup as the aluminum settles out and needs a good whipping. I sometimes mix a new tin with a drill and a paddle then put it in to smaller tins and use it from that.
    The hardener seems to not need much mixing.

    Small batches and often is the way to go so you cover nice clean steel as soon as possible, I normally do it last thing before I leave the garage at night.
    If you get accurate digital scales go to the pound shop and get 100 plastic cups for a quid.
    The paint or thinners doesn't seem to affect them and they are big enough for touch ups.

    I hope the mix ratios file is attached.
    If it isn't PM me and I'll send you a PDF or better still, someone might tell me how to attach a PDF.
     
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  15. Hudders New Member

    Messages:
    11
    Location:
    Poole, Dorset. England
    Great advice, I'm taking it all on board, I'll stick to the 87a winter as its better value and i'll get some cheep mixing pots.
    Thanks for the info on the weights.

    What do you use to clean the metal before applying the jotun? Any recommendations on the spot gun.
     
  16. bricol Member

    Messages:
    957
    N.Yorks, UK
    Eat lots of Aldi microwave puddings - the blueberry is nice :) The pots make perfect mixing cups.

    I have a couple of Aldi spot blast guns from when they were cheap - the media was pretty goods too. Unfortunately the "rubber" cups that come with them are rock hard so don't seal very well - I still use the rubber cups that came with a long deceased Machine Mart gun. Basically, for DIY use, nearly anything works.
     
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  17. Hudders New Member

    Messages:
    11
    Location:
    Poole, Dorset. England
    Eat puddings and fix cars, living the dream.

    I'm so sorry to Dcal and bricol for all the questions, I hope I'm not being to much of a pain, I'm working through it and taking all your advice on board.
    Regarding the spot blasters you both mention, do you mean the ones with the rubber cups on them such as this..https://www.amazon.co.uk/dp/B007PCB...olid=3BBFERLWIJE87&psc=1&ref_=lv_ov_lig_dp_it
    or this..https://www.amazon.co.uk/dp/B07D2B8...olid=3BBFERLWIJE87&psc=1&ref_=lv_ov_lig_dp_it
    If you use the rubber cup ones, do you find you can use it anywhere, I imagine you can't just point it at a part to clean like a crevice as it looks like it must be in contact with the area to blast.
     
  18. Morrisman

    Morrisman Forum Supporter

    Maybe a mini sandblaster, you can buy ‘spot blasters’ specifically for small areas, get it back to bare metal then decent primer on immediately.

    ETA. Beaten to it, I should read the whole thread before replying.:ashamed:
     
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  19. bricol Member

    Messages:
    957
    N.Yorks, UK

    Yep - the first one - looks just like an Aldi one only yellow - but the Aldi ones were a tenner! Surely they must be cheaper somewhere?

    And yes, press the rubber bit against what you are blasting - most of the media gets collected in the bag so you can reuse it - and it doesn't go everywhere. I found I had to run a higher pressure than the instructions claimed to get good results. Different shapes allow you to get in and seal to lots of nooks and crannies without too much lost media.

    The other gun will work - but the media will go everywhere and cover everything - not good. Works in a confined space like an empty garden shed where you can put a tarp down and collect the media for reuse.

    For big areas, or heavier rust, I bought a pressurised pot - got carried away with how good it was at getting to clean metal (underseal, paint and rust gone!) I didn't think of where the media was going . . . I'm still collecting it from shelves, tops of sockets, toolboxes, cupboards, 5 yrs later!

    For bigger stuff (front subframe from my Alfa 159) I gave it to a local blaster with 50 quid - came back perfectly clean. He was worried he'd charged me too much as it took him a few minutes - I pointed out it wasn't his time I was paying for - it was for a good job, that didn't take a day of my time, waste lots of my media or annoy my neighbours - well worth 50 quid! (I was staring it at it yesterday as I welded up a cracked front exhaust downpipe from the manifold from a rather over-exuberant overtake bottoming out on the back road a few weeks ago - still looking good in Jotun epoxy, covered in 3M uunderseally stuff, covered inside in Noxudol 700)
     
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  20. Dcal

    Dcal Forum Supporter

    Messages:
    1,820
    Location:
    Antrim Northern Ireland
    Got to agree with Bricol again.

    This is the spot blaster I have

    https://www.sealey.co.uk/product/5637198507/air-recirculating-sand-blasting-kit

    I sure as hell didn't pay that for it but the thing I like about it is the different cups which are useful for an inside corner and an edge. I still have most of them and they still work (haven't gone hard or worn away) which isn't bad as it's over 20 years old.
    Anything similar will work.

    I blasted the underside of my 75 on the lift with a pressure pot and used a geo-fabric (Terram)to keep the dust from going everywhere. It worked but was a pig of a job.
    The bother of getting it to someone to blast it put me off and I know how it's done now.

    Keep the questions coming we will help where we can.
    It's good to see someone else has the good taste (or insanity) to take on another 75
     
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