Vactan V's Krust

[lhd]

Any ideas....?
I have used Vactan and can't see any real benefits.
I used Vactan on a rusty step and within a couple of weeks it was rusting again,thats without rubbing it down.
I have now used Krust on the same area and it's as still as black as soot after the same amount of time. I'm starting to wonder if Vactan's all it's cracked up to be.
I mean how is something that you "had" never heard of be better than the off the shelf stuff?
Surely if it was that good you would think that you would have heard of it, and Halfwits/Frost would be blowing it's trumpet for them.
Rob.

[jamesc76]

I have used all sorts mainly use krust as easy to get it all depends on the weather when you put it on really! (oh and i det discounts at halfwits )

[eatcustard]

I use Oxycon
After 4 months still no rust as come back.

If you dont rub down it will come back, its still rusting underneath

[neil3965]

Vactan and Kurust use exactly the same active ingredient - tannic acid. Both are water-based.

I don't think you can usefully compare the two by applying one on top of the other - did you rub down the Vactanned step before applying the Kurust? If so, you may have removed existing rust that wasn't removed before the Vactan went on.

With these products preparation is everything - you have to carefully remove ALL loose rust, best using a wire brush on drill or grinder, then wash it down to remove salts. Then apply at a temperature above 10 deg C - the warmer the better, as the chemical reaction that converts the rust to inert tannate is temperature dependent.

[1664]

I thought both of them reacted with the rust converting it to an enamel so if you remove the rust (other than loose rust) there's nothing to react with as it'll just be bare matal - in which case you might as well just paint it

[neil3965]

I did say 'loose rust' - if there's any powdery rust and the Vactan or Kurust is not worked in sufficiently it will react with the surface stuff, leaving unconverted rust underneath.

A guy on the pistonheads.com forum did a comparison test (using Fertan, a similar product) --

"Well I was testing it last weekend, on a suspension arm that had 200,000 miles worth or road salt corrosion on it.

Surface had large rust bubbles ( 3- 4 mm )and severe flaking.

I drill wire brushed half of it.

On the whole arm, I applied 1 heavy coat of fertan and then damped it down after 2 hours with water.

After 24 hours, I washed the arm down with water.

I cut into the arm with a dremel, and using a fine grade of sandpaper rubbed the black "chelate" away to get an idea of the penetration.

On the wire brushed side ALL the rust had been converted to an inert black powder or surface.

The non wire brushed part had a total outer covering of converted chelate to a depth of about 0.5 - 0.7 mm measured on my feeler gauge, and then iron oxide to a depth of 0.4 mm underneath.

Conclusions : if you can remove the rust with a wire brush down to a level of around 0.5 mm then the conversion works very well."

No point putting it on shiny metal though - you're right, no rust to react with, might as well paint it. But it must be absolutely rust free - even the slightest pitting will retain some rust which could be the nucleus for more rot.

[1664]

(I was really referring th lhd's post when I mentioned loose rust.)

Trouble with a lot of rust (especially on the inside) is that it's inaccessible and can't be rubbed down to any extent.

[Spiral]

Used Vactan after good reports here. Spent a lot of time on preparation and 9 months later rust showing through again, so obviously very disapointed with results I have gone back to using Kurust from Halfords.