Available at Canadian Tire.  Indeed, it's called Extend, made by Duro.

Worked well for me--3 years and no re-growth.  I'd consider it a
stop-gap measure, but as stop-gaps go, I was happy with it.

T.

At 2:15 PM -0700 7/30/01, Scott LeGear wrote:
>Years ago I had some rust start to form on my then new 1977 VW Bus.  I
>applied a compound which was then pretty new, I think, called "Extend." This
>stuff was promoted as being able to chemically combine with the rust and
>stop it dead in it's tracks.  The literature said that there HAD TO BE RUST
>in order for this stuff to work, so not to use it as a preventative.  It was
>a water based stuff that you could apply with a brush.  I used it on those
>spots where rust was beginning.  It turned the rust to black and killed it.
>I kept that bus for years and then sold it to a friend who kept it for years
>more.  This was in Florida.  Those rust spots never grew.  I don't know if
>this product is still on the market and as I'm now mostly in the desert it
>is not an issue with me.  But for those with the need, I HIGHLY recommend
>the stuff.  At the time it was available at K-Mart and hardware stores
>pretty commonly and was not expensive.  I think it was made by DURO Corp.
>
>Scott

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Tobin Copley        Bowen Island, BC, Canada      49deg 23'N-123deg 19'W

'82 Westfalia 1.6L NA diesel ("Stinky")
'97 son Russell                                   =============
'99 daughter Margaret                            /_| |_L| |__|:| clatter
                             SPEED KILLS!        {.            .| clatter!
                         Drive a Vanagon diesel   ~-()-==----()-~