Are rust convertors good or useless?

[sardine]

I cant see much real use for them, unless there is an area you cannot access to wire wheel off and paint. In that case stuff like Vactan will only last a year outdoors , rain will wash it off.

I have some things in storage like crank cases and lathe parts that need the surfaces protecting and its easy to brush on Vactan and forget about it.

Someone convinced narrowboat owners to splash Vactan on everything , many of them apply it then brush it off and paint over , or apply oxide primer over it so that the primer is not in contwct with the steel and useless, One clever fellow on Youtube painted his entire hull with it under bitumin blacking, a total wast of money at £25 a litre.

 

[bigegg]

I like bilt hamber hydrate 80 - it's about the best according to multiple reviews Ive watched/read.
BUT: you need to get rid of as much surface rust as possible first - it's okay to convert the last few dark spots after most of the metal is sanded to shiny, or after acid-dipping, to get into the seams.

It's better than nothing, however.