Stopping everything from rusting.

[Martin KyteParticipant @martinkyte99762]

Posted by not done it yet on 05/12/2022 22:51:12:

Sorry, but a long way off re cement/concrete chemistry. Cement is calcium silicate based (with a few other necessary constituents) and concrete typically only contains about 15% cement. Perhaps 20% in precast thin sections.

My workshop is in a sectional concrete garage and is insulated, so definitely possible!

Yes I know but what I'm talking about is the reaction of CO2 with concrete in the presence of moisture as described here.

**LINK**

and the following :-

Calcium bicarbonate, also called calcium hydrogen carbonate, is an unstable inorganic chemical compound with the chemical formula Ca(HCO₃)₂.

The compound cannot be isolated in solid form as it decomposes to calcium carbonate and carbon dioxide upon removal of water via either boiling or vacuum drying. It exists only in aqueous solution containing the calcium (Ca²⁺), bicarbonate (HCO−
3), and carbonate (CO2−
3) ions, together with dissolved carbon dioxide (CO₂). The relative concentrations of these carbon-containing species depend on the pH: bicarbonate predominates within the range 6.36–10.25 in fresh water.

came from here

**LINK**

regards Martin

[Dave HalfordParticipant @davehalford22513]

All I can say is in an integral garage where rusting is not an issue, painted 3 draw cabinets rust where they touch the bare 1980's concrete. A piece of old carpet stops it.

[VicParticipant @vic]

Posted by Grindstone Cowboy on 04/12/2022 15:55:07:

I know this isn't going to help much, but I had one of those garages at a previous house and it was the worst thing I've come across for stuff rusting.

Possibly making an insulated ceiling and insulating the walls may help a bit, in effect creating an insulated inner box that you can heat / de-humidify more easily.

Rob

Yes same here, I had one. I started keeping a lot of my tooling in clip lock boxes to stop them going rusty. Oil or grease on some of the big stuff if I wasn’t going to use it for a while.

[File HandleParticipant @filehandle]

Martin
I think that you are confusing what happens to steel reinforcing in concrete with rusting away from the concrete. The water in the air will be mildly acidic due to dissolved CO2 forming a weak solution of carbonic acid.. The acidity is caused by hydrogen ions not the bicarbonate. The pH you quote is referring to the disasiciation of the calcium bicarb, not its pH per se.
As others have said rust formation needs oxygen and water, removal of either prevents rust. My asbestos garage is lined with a timber lining plus a bit of insulation, bur I find a liberal coating of oil prevents steel from rusting.

[Nigel McBurney 1Participant @nigelmcburney1]

with insulated double skin,block all holes in the exterior skin to keep mice out,they love the warm cavity and ruin the insulation.

[File HandleParticipant @filehandle]

Also if it is timber lined this needs painting to prevent the timber being a source of humidity.

[Martin KyteParticipant @martinkyte99762]

Posted by Keith Wyles on 06/12/2022 15:33:12:

Martin
I think that you are confusing what happens to steel reinforcing in concrete with rusting away from the concrete. The water in the air will be mildly acidic due to dissolved CO2 forming a weak solution of carbonic acid.. The acidity is caused by hydrogen ions not the bicarbonate. The pH you quote is referring to the disasiciation of the calcium bicarb, not its pH per se.
As others have said rust formation needs oxygen and water, removal of either prevents rust. My asbestos garage is lined with a timber lining plus a bit of insulation, bur I find a liberal coating of oil prevents steel from rusting.

Yes I get that, and I’m not talking about the reinforcing but the generation of calcium bicarbonate by the reaction of atmospheric CO2 with the cement. As far as I can make out calcium bicarbonate can only exist in solution and as it dries it evolves CO2 which will acidify the solution by producing carbonic acid. So maybe concrete under cyclic dampness can act like an acid pump periodically creating a more than usual corrosive atmosphere. All this is just a hunch based on the anecdotal statements about concrete garages being the worst for corrosion. I need to ask a professional chemist really. These types of garages are bad for corrosion just because of their construction but it’s worth figuring out if there is something else going on. I will ask a chemist.

regards Martin

[Martin KyteParticipant @martinkyte99762]

So I asked a professional and basically I'm chasing a non existant problem and talking a lot of tosh. Concrete does not chemically add to the rust problem of concrete garages which is nice to know and those of you who suggested such were correct.

regards Martin

[not done it yetParticipant @notdoneityet]

Posted by Martin Kyte on 08/12/2022 11:38:59:

So I asked a professional and basically I'm chasing a non existant problem and talking a lot of tosh. Concrete does not chemically add to the rust problem of concrete garages which is nice to know and those of you who suggested such were correct.

regards Martin

Thanks for your findings. I actually analysed cement for about 3 years from late ‘69 (and occasionally concrete, too). That was predominantly wet analysis (XRF and XRD followed, as analytical methods progressed to more automated/advanced methods). Other lines, of mine, were recovery of precious metals Silver, gold, Platinum and Palladium, mainly), supply of aromatherapy-type ‘concoctions’ (oils, creams and other sundry products) and analysis of radio-isotope products (for both radioactivity and chemical purity).

Calcium ions are quite electropositive in nature and there was generally less than 3% ‘free lime’ (as CaO) in most cements (maximum amount varied depending on the source) but excessive amounts cause expansion as the cement cures (hydrates). Even at a 5:1 aggregate to cement ratio that small percentage of free lime would account for less than 0.5% of the concrete and would typically be converted to calcium carbonate early in its life. Concrete cover is used, as the only means of preventing reinforcement corrosion, in many structures.

Thin sections, such as in fence posts and garage panels can last decades without problems. Then there are the more specialised cements such as High Alumina and Sulphate Resisting. Quite a complex area in its own ‘niche’.🙂

[Chris123Participant @chris123]

Thanks all.
I’ll read though and decide what to do.

Chris

[vic neweyParticipant @vicnewey60017]

It's strange but I have a draughty 14X8 ft wooden lean to shed against the house, the floor is paving slabs , roof is corrugated plastic with shading screens, there are four vintage lathes, loads of tools etc and more or less nothing rusts at all.

Only problem is sometimes in Spring on a warmish day condensation can drip a few drops but this rarely happens

[Tim StevensParticipant @timstevens64731]

The mention of reinforcing steel in concrete is a further clue to the problem. the reinforcing adds two new causes of condensation – first it allows the concrete to be thinner so less insulating, and the steel conducts heat through it so even less insulating.

I now realise that although the Welsh Marches is not always a very good place to enjoy a garage hobby, it has one major advantage. We are only about five miles from a Kingspan factory. And they have off-cuts and rejects …

Cheers, Tim

[John AbsonParticipant @johnabson65530]

Interesting to read this thread and the many words of wisdom. If I may add a few comments of mine, even if not very wise :

Insulation: a key to avoiding rust is avoiding condensation, and the key to that is avoiding rapid temperature changes. Insulation slows down the rate of heat transfer and thus temperature changes and avoids condensation on surfaces where there is a temperature difference. It also helps a great deal in the summer, especially with roof insulation which avoids the effects of direct sunlight beating down on it.

Spray foam. Anyone who instals that is signing a pact with the devil. Yes, it insulates, and is easy to apply. After that, it's a nightmare with entrapped moisture, lack of ventilation, outgassing of nasty chemicals and difficulties in building maintenance. Slab foam or rockwool insulation is a much better way to go.

My own workshop is a reasonably substantial timber shed with 50mm of Rockwool RW4 grade** covered with 13mm OSB (Sterling) board panels for the walls and ceiling, which make for easy attachment of storage shelves, small tool racks etc. The floor is timber, laid on concrete slabs bedded on a very light dry sand/cement mix. Machines are mounted on anti-vibration pads through holes in the floor, resting on the concrete slabs underneath. A couple of holes at rafter height allow a through flow of ventilation which helps reduce humidity build-up.Windows are 'economy grade' commercial timber double glazed units.

A number of people have mentioned roofing felt; Onduline corrugated reinforced bitumen panels over battens laid on OSB panels are far more durable and easy to replace when eventually needed. The air space in-between adds to the insulation effectiveness. Sold at Wickes.

Heating is a small and simple oil-filled radiator with a thermostat.

It makes for a most comfortable working environment and even in recent -8C external night time temperatures was a pleasure to work in with the timber floor being easy on the feet and legs.

In your case, I would line out the concrete garage (internal shed approach as suggested) and insulate.

/John

**Rockwool in the more technical grades is available from Rockwool distributors over the counter, often a wider range than the usual DIY 'sheds'. Rockwool have a very helpful technical helpline. Google is your friend here.

Edited By John Abson on 18/12/2022 11:29:36

[Pete RimmerParticipant @peterimmer30576]

Just a warning to everyone today. My workshop is very well insulated (it's built from metal clad insulated panels) and I've never had the least bit of problems with condensation. Today's 14 degree rapid rise in temperature has actually made the ceiling damp and put a fine damp film on the stuff in my workshop and I've had to spend time wiping stuff off and applying water displacer to make sure noting rusts. Never had to do that since I built the place in 2008 but today is rather unusual circumstances.

I would advise anyone to go out and check their workshop over if they have bare metal they don't want rusting over.

[Howard LewisParticipant @howardlewis46836]

My shop is 10' 9" x 6' 9" exterally, with 19 mm T&G cladding on 50 mm frames with 12mm ply inner. The gap is filled with glassfibre. The roof is 12mm ply on 50 mm frames, with 12 mm ply inner, again filled with glass fibre, now topped by a rubber membrane..

On the rear wall there is a high level, hooded, fixed vent (Actually a 6" ex equipment fan ) At floor level, there are two small, about 50 mm diameter fixed vents.

The floor is 19mm ply, supported on 8 x 2 bearers, which are shrouded on three sides, (Fence and low walls )

Condensation / rust has been no problem since it was built 19 years ago.

When it is cold, a thermostatically controlled 2 Kw heater runs for about 15 mins and then cuts in again about 45 – 60 minutes later, for a short time.

This is in East Anglia, U K.

Unless the weather is wet ans/or cold, often the door is left open.

When it is frosty, a 80 watt tubular heater, under the fitting bench is switched on, as a precaution.

The lack of rust problem is ascribed to good insulation, and good, but not excessive ventilation.

Howard

[GaunlessParticipant @gaunless]

Pete. You have done me a massive favour! Read your post and went straight out to check my lathe. Horror! Surface rust! Wiped it all off with an oily cloth, but if I'd left it much longer there'd have been trouble. You've saved my bacon! Thanks fella!

[Ches Green UKParticipant @chesgreenuk]

Pete,

Just a warning to everyone today.

Same here Pete, in central Scotland.

My shed has been 0-3C for about a week but this morning (- outside temp was about 10-12C and humid) I went in to the shed and saw that everything was covered in condensation….even the undersides of wooden shelves!

It would seem that my reasonably well insulted shed had remained very cold inside. Meantime outside, the air had quickly become warm and humid. As soon as I opened the shed door the damp air entered.

I've never had bad condensation before so I think this is a rare event due to the large and sudden temperature delta. But I've now bought a small bar heater for 'next time'. I'll turn it on a day or two in advance when I see large temp rises predicted.

Ches

[Pete RimmerParticipant @peterimmer30576]

I've had the de-humidifier running for 2 hours it's pulled a litre of water out of the air. I've left it running in there for the night.

I'm so glad that I caught this in time I have a lot of scraped stuff including straight edges and reference squares that would all need re-scraping if I hadn't. Not to mention the machine tools themselves.

[Henry BrownParticipant @henrybrown95529]

Put my dehumidifier on yesterday afternoon for a couple of hours thinking it would do the trick, checked just after lunch and there was lots of moisture on anything big and metallic so wiped all the moisture off and set the dehumifier for three hours. Just checked humidity down to 60% and about 2l of water in the tray. My workshop is sectioned off in a corner of a large double garage, fortunately the car in there was fine.

[Ches Green UKParticipant @chesgreenuk]

In anticipation of the cold spell I had wiped way oil (forget the actual brand) on anything metalic I could find in the shed, so the condensation was sitting on the oil this morning.

About noon I reckoned the only way to get the condensation off the metal was to aim a hot air blower at the lathe, mill etc to try to bring them up to ambient temperature. That seemed to have worked somewhat, as most (but not all) of the condensation was gone – the shed has four vents so hopfully the gentle flow of air through the vents would carry out the evaporated moisture in the warm air.

I'll check tomorrow for any rust patches and treat them.

Ches.

[James AlfordParticipant @jamesalford67616]

I had condensation in my newish garage for the first time yesterday. About nine large pots of paint were standing together under a table, each of which was covered in heavy condensation. A car engine that I am building had a much lesser amount on it, but everything else was dry. Odd.

James.

[not done it yetParticipant @notdoneityet]

Judicious use of a chinese diesel-fired air heater, and running my dehumidifier on low power for one hour each night, has kept my workshop above 5 degrees and below 60% humidity throughout the cold snap.

It has required about an hour run on a fairly low setting on the 4(?)kW heater once or twice a day. Far cheaper, for me, than running the dehumidifier(s) for longer, or on high power.

Sometimes warmed while I am in residence and sometimes just started and left to shut itself down after a one hour run.

Back to just the dehumidifier at present. So costing about 7p per day again – for a few days at least!

[vic neweyParticipant @vicnewey60017]

After me bragging that my unheated draughty shed never gets my tools rusty I got a shock yesterday when I found the lathes on one side of my shed covered in condensation.

The side joined to the house towards the door was the worst. the lathe farthest from the door unaffected.

The opposite side of the shed with an Emco miller and South Bend lathe had no condensation whatsoever! Never seen anything like it in the 22 years I have had the shed.

[BazyleParticipant @bazyle]

Vic, the wall by the house would be warmer so a very slight rising air movement pulls any damp new air to that side of the garage. Sounds like the condensation inside a jar we were discussing a few weeks ago.

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