It's Oxalic-time again!

[VicS]

Re: It\'s Oxalic-time again!

[ QUOTE ]
through rhubarb stalks

[/ QUOTE ] Another opportunity to post a link to this wonderful site

The Rhubarb Compendium

 

[Vara]

Re: It\'s Oxalic-time again!

Re oxalic/aluminium.

Just a little test, alumium foil in hottish saturated oxalic soln.

Before

During

After

No discernible attack in half an hour.

 

[Krusty]

Re: It\'s Oxalic-time again!

A word of caution following the reference to 'Mosaic tile cleaner'.
It may well be similar to the 'Brick Cleaner' sold here by builders merchant. Its active agent is hydrochloric acid: seriously corrosive to almost all metals and probably damaging to glassfibre and most boat components (and skin).
If Oxalic were a nail-file, Hydrochloric would be a road-ripper!

 

[jimbaerselman]

Re: It\'s Oxalic-time again!

[ QUOTE ]
If Oxalic were a nail-file, Hydrochloric would be a road-ripper!

[/ QUOTE ] Just try dipping an old stainless steel kitchen knife into hydrochloric acid! It goes all dull. And whether it's still stainless, we'll wait for some old chemist to react . . .

 

[alahol2]

Re: It\'s Oxalic-time again!

Talking of old chemists....
Is there one on the forum who can suggest how to make the gel type carrier for oxalic acid? Walpaper paste is easy and cheap but if it dries it can be a real pain to get it off.

 

[vyv_cox]

Re: It\'s Oxalic-time again!

Sorry, an old metallurgist has reacted instead! (or maybe as well)

The composition of so called 'stainless steel' cutlery varies enormously, 400 series with usually 5% or 11% or 13% chromium to 300 series with 18% chromium, 8% nickel to the best grades available nowadays, something like 20% chromium 10% nickel. Chromium gives corrosion resistance, so the less there is the more likely it is to be attacked. Cheap cutlery is often the 5% stuff and I would expect that to be tarnished and maybe surface pitted after exposure to HCl. Refinery compressor piston rods, that see lots of HCl, are usually made from 13% chromium steel and they last for many years without problems.

For really long-term exposure to chlorides the problem becomes not surface tarnishing but pitting. This is far more harmful, so for components expected to have to resist it, 2% molybdenum is added to the 300 series. This is the difference between 304 and 316 stainless (A2 and A4), the 316 has the molybdenum.

 

[jimbaerselman]

Re: It\'s Oxalic-time again!

Thanks. Fount of knowledge, as usual!

 

[Vara]

Update Oxalic v aluminium

After two days immersion, foil reduced in size by about a third and crumbly mess left;

So prolonged exposure not a good idea!

 

[Vanilla]

Re: Update Oxalic v aluminium

What a neat little experiment. Thanks for that

 

[sparkie]

Re: It\'s Oxalic-time again!

At risk of repeating myself............ Harpic blue toilet cleaner and limescale remover does a great job. Cheap, no mixing, no messing about, no potential damage, just wipe it on, leave 10-15 mins, wash off. Bingo! All yellow stains gone. Polish with car wax, entire job 1 hour tops.

Safe sailing

Sparkie

 

[VicS]

Re: It\'s Oxalic-time again!

Harpic blue toilet cleaner and limescale remover

has list of precautions on the label as long as your boat

contains hydrochloric acid

Will leave your boat smelling like a lavatory! A clean one admittedly /forums/images/graemlins/grin.gif

 

[sparkie]

Re: It\'s Oxalic-time again!

Hi Vic, yes that's the only downside. However, as I'm only using it on the outside, and then leaving it on the car park for six months it doesn't really matter. The smell goes in a couple of days anyway. Been using it now for three years on my painted hull and never had a problem. Quite the reverse, finish is still great.

Cheers

Sparkie