Hi.
This weekend, I’m getting my car up on ramps and going to wire brush the under-side, prior to a coat of Shultz or something similar.
I’ve been recommended to coat with Hydrate 80 before underseal / Shultz but some reviews talk of rust appearing as the Hydrate 80 dries (Apparently it’s Water Based)
What have you guys used to turn your rusty underside to solid metal before sealing it with . . . . . . ?
thanks
Read the instructions with the hydrate 80 and the temperature not to apply below.
The steel then needs primed and top coated before applying rustproofing goo.
As always with any painting system, following the manufacturer’s advice and preparation is key.
I use aquasteel and check it every year. But they tend to rust from the inside out so you I inject Dinitrol ML into the box sections. While underneath check the underseal as it has a habit of rusting from underneath and falling off.
Every one who works with MX5’s finds that the stonechip applied at the factory disbonds over the years and allows water to be trapped between the steel and the disbonded stonechip, with the resultant corossion and now we have Raymond above reporting this finding.
There is a member of this forum who believes he knows better on virtually every aspect of MX5ism and states this “Does Not Happen”. I’m afraid Raymond you have joined the ranks of those who like myself who are spreading “Fake News”.
Good post Raymond.
On mine, I found that the underbody coating had flaked mostly at the seams, joints and sharply curved areas.
I scraped everything away at those areas, as far as possible till I found clean metal.
I applied Kurust.
Then 2 coats of a marine resin/zinc primer, Bondaprimer.
Then 2 coats of dark grey chassis paint.
Then Waxoyl on top of that.
I check every autumn, and re-apply Waxoyl where necessary.
I try to steer clear of underseals…, they hide too much.
Hydrate 80. I see that name floated around quite a bit.
Never used it, but note that much of the advettising blurb says that it contains no chlorine from hydochloric
acid… which casues problems etc. Must say, I’ve never heard of hydrochloric acid being used in rust converters.
The most common are tannic acid, and phosphoric acid.
They all convert the top thin layer of rust into an inert iron compound.
'Spect Hydrate 80, under the pseudo-scientific blurb…
is much the same.
Hydrate 80 was recommended to me by Chris at MX5 restorers. Since that recommendation I have cleaned up the underneath of our aged Eunos and my not so aged but probably more rusty Golf. Very pleased with the results and numerous other jobs done with it. Underneath of cars has stayed remarkably rust free after a couple of years
After I get over the cambelt/waterpump/seals. etc job just done will do my 1997 MK1 too.
I just overpaint with smoothrite black or similar, might end up with rustins this time and then waxoil underseal(stays flexible) where required.
As above really with the Bilt Hamber products.
Certain areas on the Mk3 were never protected fully from new, I found them to be around the rear wheel arches in front of the wheel and also going underneath the car along the rear part of the sill. Other areas I’ve found or course prone to catching the road muck and then rusting, it would of course apply to any model you have just treat and protect.
The products I used were Hydrate 80 and black epoxy mastic from Bilt Hamber. I’d been through a number of car resto projects, various websites and recommendations and they all seem to have their favourites, I settled with the above.
First pic I treated the areas with the Hydrate 80 after removing the rust. 2nd pic applied the epoxy mastic. 3rd pic overpainted with black hammerite for good measure.
I did other areas too but you get the idea with what’s shown.
Just to add to the above post, the epoxy mastic is potent stuff, wear a mask, eye cover and gloves as recommended.
I had previouly treated the undersides with Kurust and Dinitrol but I could see evidence of rust creeping through again after 2 years. It was nothing drastic ceratinly not crusty stuff just surface, maybe my previous pre prep wasn’t good enough. The latest treatment involved prep with flap and grinding wheels to really get into the metal and remove as much rust as I could.