oxalic effect on good bores and tappet guides?

[JonE]

I've been having good results using oxalic acid on rusty parts thanks to recommendations on 'ere. 
I've got a good block that I am stripping down to check everything and I don't want to remove the bronze guides for tappets and valves.

I've taken the core plugs out and the side outlet is off... and I'm now realising that its going to be difficult sealing all the holes to "fill it up" with cleaning solution.

In the past, I've sealed up everything so the clean is internal.
 
What would the effect on studs, good bores (a couple of dark stains only) and bronze guides be if I were to soak the entire block with everything in place? Inadvisable?

[Hedd_Jones]

I would not trust it on good machined surfaces Jon

[JonE]

ok - I need to think of another way. Was going to block up everything with siliconed-on sections of perspex, but then realised I had the 3 side branches holes as well!

["Slack Alice" Simon]

Hi Jon.

I use good old-fashioned Plasticene for this kind of job - in my case, sealing drain holes in hollow boat trailer members before filling with anti-rust goo.

[Bruce Young]

What about using molasses? I have been soaking stuff in 10%. Often works and seems to do no harm. Bruce

[JonE]

I've got a two litre bucket of Oxalic now, so.... may be off mollases for some time!

I've proceeded with glazing all the side orifices - decided they needed to be strong albeit temporary - and will commence a fill tomorrow. I have a cunning plan to blow down a straw through the block-to-head holes to disturb the thick layer of lemon yellow sediment which develops on the active surfaces. (I haven't worked out whether its presence actually stops the rust-eating process, or whether it just seems like it might).

[Robert Foreman]

All you need to do is fit a blocked off side water branch. Set the block level and fill up to just below the top face.

[JonE]

core plugs...! yes I know I should have taken them out later, but didn't think it needed doing until...

[Stuart Giles]

Oxalic acid only attacks rust, it doesn't have any measurable effect on good metal. Amongst many other iron and steel bits, I have used it on a Jones and Shipman tool/cutter grinder that I bought for scrap money with a seized column. After using a 30 ton press to remove the column from the machine, it went in an Oxalic bath for a few days.

Before:



After:



There is staining where the Oxalic acid has removed the rust, but there has been no effect on what was clean metal. This column (which elevates the grinder's wheelhead) is a precision fit in the machine; following this  treatment it still has an accuracy well inside a thousanth of an inch.

[Dave Mann]

    This is my method of removing all the debris from the block and head using Deox C circulated in the reverse direction by a washing machine pump in the white bin and the blue bin acts a sump to collect a vast amount of debris. I run the pump for a few minutes then shut the valve and stop the pump to let it stew for a few hours before restarting it.