On Tue, 27 Mar 2007 20:51:00 +1200, Eric Stevens
wrote:

On Mon, 26 Mar 2007 17:56:36 GMT, "Gordon Wedman"
wrote:


"Peter Hendra" wrote in message
. ..
On Sat, 24 Mar 2007 12:44:13 GMT, Rich Hampel
wrote:

Probability is that the welds are not ground flat and smooth and
crevice corrosion is underway in the 'intersticies' of the weldment
(poor weld technique ... not a full penetration weld).

To be 'corrosion resistant' (chlorides, etc. attack stainless) all the
weld must be flat /smooth by grinding and then polishing/buffing to a
high mechanical mirror polish. Any 'weld-lap' or pin-hole in the weld
will be a source of 'rust' .... gotta be closed and then smoothed. .


This has just made sense as only one of the bolt on "feet" for the
ladder suffers from the problem. I'll try it.

Thanks very much to all who responded.

regards
Peter Hendra

A friend has gone thru this with his stainless. People at his workplace
that know about his sort of thing told him he needed to passivate the welds.
They gave him some solution to paint on the welds. I believe this is
hydrofluoric acid, perhaps a mixture with other acids. Requires very
carefull application. It took away the surface shine. Don't recall the
final result but I can ask him.

It won't be Hydrofluoric Acid, which is one of the nastiest nasty
chemicals on the face of this earth. It's much more likely to be a
50~50 mixture of Hydrochloric and Nitric acids plus, sometimes, a
little Phosphoric acid. You should somewhere find an expert and read
http://www.assda.asn.au/asp/index.asp?pgid=17982
Whatever you do, you don't want a strong brew and you should let time
be your friend.



Eric Stevens

Thanks Eric,
A great site and I love your phrase "let time be your friend" -
poetic. May I have your permission to use it in future - yes, I'll
cite you as the originator? I don't want to get flamed.

cheers
Peter