WIX Archives
Re: Corrosion Issues...
Posted by John Parker on Thu Aug 07, 2003 08:04:26 PM
In reply top Re: Corrosion Issues... posted by Dave Robinson on Thu Aug 07, 2003 07:05:37 AM
: : : John,
: : :
: : : I saw in your post that you have information on saltwa
: te
: : r
: : : & corrosion...do you have any information on fresh wat
: er
: : a
: : : nd shallow wrecks? What are the problems faced when t
: he
: : se
: : : are recovered (if any). There are numerous recoverie
: s
: : of
: : : fresh water wrecks and their condition is amazing but
: I
: : h
: : : ave yet to come across the issues they faced after rai
: si
: : ng
: : : them and during restoration...
: :
: : Hi Dave
: :
: : The simple answer is that there is no simple answer!!!!!
:
: :
: : Whilst it is true that salt water is much more of a prob
: le
: : m than fresh this not the only factor. Corrosion occurs
: in
: : all water and in the air for that matter. The main issu
: e
: : other than salt water is the chemical composition of the
: w
: : ater in general. Fresh water can be corrosive if the PH
: ba
: : lance is too acid or alkaline for instance or if the wat
: er
: : contains corrosive chemicals or minerals. You often hea
: r
: : that an aircraft recovered from water is put into a bath
: o
: : f fresh water for a time before it is worked on- this is
: l
: : argely in an effort to stop the process of corrosion and
: r
: : emove any build up of corrosive material.
: :
: : A couple of other factors involved here are the fact tha
: t
: : a wreck also rests on the floor of a lake , river or the
: s
: : ea and the composition of the sediments it is in contact
: w
: : ith here are another problem as the water may be OK but
: th
: : e mud rots the parts it is in contact with or visa versa
: .
: :
: : I am no expert on any of this but generally anybody who
: ha
: : s been involved will tell you that the sooner you can ge
: t
: : a recovered aircraft treated, cleaned and properly disma
: nt
: : led the better the chance of a high quality restoration
: ar
: : e with the smallest loss of material. Exposure to air wi
: th
: : out treatment straight out of water hastends the corrosi
: ve
: : reaction as oxygen accelerates the process. Unfortunate
: ly
: : this is exactly what happens in countless cases and a g
: re
: : at recovery often turns to powder in a short period of t
: im
: : e. I think this is what is worrying a lot of people abou
: t
: : the Brewster Buffalo recovered in the lake a few years b
: ac
: : k as it is still sitting around.
: :
: : I will try to get you some whitepapers from a couple of
: Un
: : iversities here in Australia that I have read that might
: b
: : e of use to read.
: :
: : Regards
: : John P
: : :
: : : Cheers
: : : Dave
:
: John,
:
: Although you say you are not an expert do you happen to kn
: ow what affect a thin coating of oil applied to an airfram
: e will have on the corrosive process? Will this slow it d
: own and buy time for the aircraft?
Hi Dave
Thanks for your question
Generally speaking and putting this in terms I understand, I am told by metalurgists / engineers that excluding access to oxygen and corrosive elements is critical here BUT some other critical issues are:-
1) There is no point painting oil or anything else over active corrosion as the process will continue under the coating. The surface needs to be cleaned down properly first and any corrosion neutralised/treated then coated with an appropriate agent with the correct chemical balance. Believe it or not some oils and wax solutions are actually corrosive in the long term.
2) Coating surfaces with just any old stuff may damage the surface ( paint and markings ) and make it impossible to preserve the surface which may be critical for a museum preservation ( The AWM Beaufort is an example of trying tom preserve as much of the original finish as possible , and a great example it is, see their site)
So the short answer is yes but it needs to be done properly and only after a proper cleaning has been done and corrosion neutralised. Then the correct product applied.
You could ask the RAF museum or the AWM in Canberra what they use as a coating - they may not use anything but I suspect they do - Hendon obviously sprayed something all over the Halifax.
Kindest regards
John P