Need some thoughts on internal engine block rust

[lars49]

It was warm enough today to get into the shop.  I've had the block covered with a plastic sheet since the early fall.  When I pulled the sheet off I found some light rust  - not heavy, more like a very light dusting - on the top of the block in the oil gallery.

I checked the cylinder bores etc, and I don't have rust on any of the bearing surface, just this one place.

So my question is what should I use to remove the rust?  I was thiniking of light steel wool but I am concerned about bits breaking off in the rough parts of the casting.  A wire brush cant't get ito the small nooks and crannies.  I thought about naval jelly, but then you have to neutralize it.

Any thoughts?

[roverman]

You "might" consider rust convertor, by Krylon/etc.  roverman.

[BlownMGB-V8]

Oil it first to contain any powder. Wipe up what you can with an oily shop rag. For tight areas I have cut a single wire bundle from a wire brush and put that in the handle of an acid brush and crimped. If that doesn't get it off the rest isn't going anywhere.

Jim

[lars49]

Well, I just looked at the MSDS for the Krylon product, it is a mixture of ether, acetone, and a surfactant --  2-Butoxyethanol.  My chemistry is a bit rusty, but I don't see any of those ingredients as a "converter".  

I'll try Jim's method and there is always Glyptal.

[BlownMGB-V8]

The active ingredient in most rust treatments is phosphoric acid, but it forms a byproduct (iron phosphate maybe?) that can come loose, particularly if the acid does not get all the way to the bottom of the rust. Once you have everything off that can be gotten with the wire brush the phosphoric acid (available in gallons at the hardware store) can convert what's left into an acceptable primer for glyptal, but leaving it on until it dries leaves a residue that is messy to clean up. So I'd brush it on, leave it a few minutes and wipe it off good, then come back in a day and see if it has turned purple or black. For glyptal you really need a very clean and oil free surface. Anywhere the block has been oiled I would not trust it. The whole area will be awash in oil anyway so what little rust remains isn't going to spread.

Jim

[lars49]

Phosphoric acid is tough to find here.  I found that True Value will ship it to their stores, but the closest is 2 counties away and you need to buy a 5 gallon bucket.   All the independent hardware stores here are affiliated with Ace and they claim they do not carry it.  Grainger does carry a technical grade for $35 per liter plus shipping.

It decided to drop down into the single digits last night so I won't be able to get into the shop for a while

[BlownMGB-V8]

Did you try Lowes?

Jim

[roverman]

Correction, Rustoleum makse a rust convertor.  Ooops, roverman.

[Moderator]

I think the 12oz bottle of phosphoric acid I bought last year was marketed as soldering flux. I bought it from McMaster Carr to use with silver solder on a stainless steel shower curtain rail I fabricated to go over our clawfoot tub. I don't recall what I paid, but I don't think it was extravagant.

[lars49]

No luck at Lowes, but Home Depot has Klean-Strip Prep & Etch $15.78/gal  30-40% phosphoric acid.

[DiDueColpi]

Larry,
Just wander down to your nearest machine shop or engine builder and get the block "tanked" or pressure cleaned.
All the rust will be gone and you can start fresh with no worry's
Cheers
Fred

[lars49]

Fred,

Actually I did.  I brought the block back and covered it up with a plastic sheet, and when I removed the sheet to work on the block I found the rust.  I am loath to go through that again.

[JHerscher]

If you decide on it, Ospho is a rust converter- available for about $10 for a liter at Ace Hardware.
John

[MGBV8]

Rust converters for a little surface rust in the intake valley?  Spray it with some Kroil or PB Blaster, scrub it with a 3M Scotch-Brite pad, wipe it up with a cloth rag, smear a bit of oil on it, and forget it.

[flitner]

Get some sulfuric acid to brush into the area, then neutralze it with baking soda and water, hit the whole area with your favorite degreaser, then dry it out well having some mineral spirits on hand to wipe down the bores and journal registers.

[DiDueColpi]

Hey Larry,
If you don't want to get the block re cleaned at the machine shop. Grab some Mag Wheel cleaner (hydroflouric acid) and a paint brush.
Scrub the area down and rinse off with plain water. Dry the block off and oil it down right away with WD40 or something similar to stop the rust from returning.
Do not re-wrap the block in plastic as it just traps moisture in. I've had good success with old bath towels to wrap up engines etc.
The lovely Lynne is always redecorating so there is an abundant supply of the wrong color towels. That way I can "help her out" and benefit myself.
Cheers
Fred

[roverman]

Dessecant bags ?

[lars49]

It is interesting, in that the relative humidity since I draped the plastic over the block has been in the 5-20% range.  I would have thought with the humidity that low, that I would not have seen the results that I did.  What is curious is the rust in the valley only and not anywhere else.

I was planning on working on the block this weekend since we have been in the 60's the past few days, but it looks like a storm is coming through that is supposed to dump anywhere up to 8 inches on us Saturday & Sunday.

[BlownMGB-V8]

Any temperature change will cause condensation and the plastic prevents escape.

Jim