The Triumph Dolomite Club - Discussion Forum

The Number One Club for owners of Triumph's range of small saloons from the 1960s and 1970s.
It is currently Sat Feb 27, 2021 12:01 am

All times are UTC




Post new topic  Reply to topic  [ 3 posts ] 
Author Message
 Post subject: Rust converters useless?
PostPosted: Mon Jan 04, 2021 3:23 pm 
Offline
Future Club member hopefully!
Future Club member hopefully!

Joined: Mon Dec 03, 2012 6:04 pm
Posts: 1287
I base this on a hole i found on the Dolly scuttle. Couldn't work out where water in the footwell was coming from, no bubbles, obvious signs of corrosion. So ground off the paint where I thought it might be getting in and noticed a black patch next to the windscreen surround panel. Hit it with a hammer, dirty great hole.

Had a similar thing on a Rover 75 sill. Thought I had got rid of all the rot, only the welder wouldn't arc. So hit that with a hammer and managed to knock off a huge amount of black material. The whole panel had turned to black oxide. What does this have to do with rust converters?

Well rust converters work by turning red oxide into supposedly more stable black oxide, which forms in a low oxygen environment. The problem is, I have seen more than one panel where black rust has perforated the whole panel and left a hole. It looks solid, but hit it hard enough or prod it hard enough, it falls to pieces.

This makes me suspicious about the effectiveness of rust converters. Sure they may well stabilise the paint work and prevent unsightly bubbles but that doesn't mean that the metal underneath isn't slowly being converted into black oxide.


Top
   
PostPosted: Mon Jan 04, 2021 4:13 pm 
Offline
TDC Member

Joined: Sun Oct 26, 2008 7:26 am
Posts: 2207
Quote:
I base this on a hole i found on the Dolly scuttle. Couldn't work out where water in the footwell was coming from, no bubbles, obvious signs of corrosion. So ground off the paint where I thought it might be getting in and noticed a black patch next to the windscreen surround panel. Hit it with a hammer, dirty great hole.

Had a similar thing on a Rover 75 sill. Thought I had got rid of all the rot, only the welder wouldn't arc. So hit that with a hammer and managed to knock off a huge amount of black material. The whole panel had turned to black oxide. What does this have to do with rust converters?

Well rust converters work by turning red oxide into supposedly more stable black oxide, which forms in a low oxygen environment. The problem is, I have seen more than one panel where black rust has perforated the whole panel and left a hole. It looks solid, but hit it hard enough or prod it hard enough, it falls to pieces.

This makes me suspicious about the effectiveness of rust converters. Sure they may well stabilise the paint work and prevent unsightly bubbles but that doesn't mean that the metal underneath isn't slowly being converted into black oxide.
There is more than one type of black oxide!
iron oxide is rust. Can be red, can be clack as there are a couple of types (chemically)
rust converters react with iron oxide to form Iron Phosphate. Totally different stuff. And pretty stable. Obviosuly will need painting etc, but rust converters do work.

As an aside, they are not miracle workers. As much rust should be removed by mechanical means first, leaving as clean a surface as possible. Then apply the converter to do the last tiny bit. It won't work on rust scabs/scale/flakes etc.

_________________
Clive Senior
Brighton
Driving Toledo fitted with slant 4, sprint OD box and axle. Needs fettling!


Top
   
PostPosted: Mon Jan 04, 2021 5:20 pm 
Offline
TDC Member
User avatar

Joined: Mon Nov 07, 2011 9:57 am
Posts: 674
Location: Dorset
Mostly (as cliftyhanger says) it's lack of prep. Also, treating the rust on a panel that's too far gone just leaves you with a black panel that's still screwed. Always remove everything back to clean metal, then (if there is enough solid panel left) brush on to get the bits your wire brush/grinder etc can't get. Kurust seems to work well for me.

Steve


Top
   
Display posts from previous:  Sort by  
Post new topic  Reply to topic  [ 3 posts ] 

All times are UTC


Who is online

Users browsing this forum: No registered users and 1 guest


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
Powered by phpBB® Forum Software © phpBB Limited