Rust prevention on cast iron

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Chilihead

New User
Chilihead
Hey folks,
I'm curious how you protect your cast iron tops on machinery. I saw the FineWoodworking article where they tested different rust inhibitors. For those of you that use one of these spray on products, do you paste wax after you apply this or just use the spray? Seems like the wax would help make a slick surface, but would hinder me applying more spray in the future. How do ya'll handle it? Thanks!
 

SubGuy

Administrator
Zach
Boeshield T9 works great for me. My shop is not air conditioned and it has a few large drafts. It gets quite humid in the shop in summer. I think the biggest thing is getting rid of ALL rust first then applying a good rust inhibitor. I apply no wax with Boeshield.
 

chris_goris

Chris
Senior User
The best prevention is to avoid rapid temperature swings. When you have a cold shop, your cast iron gets cold, then as we so often have in NC, the temp suddenly spikes along with humidity it seems, and Voila!, you suddenly have soaking wet cast iron because it stays much colder than the ambient air. When it has been cold and all my equipment is cold and the temp surges, I try to heat the shop gradually , allowing the tools to acclimate slowly. All that being said, a climate controlled shop is really the best answer. For those of us that don't, Johnsons paste wax is my go to top coat.
 

red

Papa Red
Red
Senior User
In my shop I keep either the heat or ac on all the time. I have a mini split in the wall and that also circulates the air 24/7. I keep all my equipment waxed and don't have a problem. I've never used any type of spay (like Boeshield T9) on my equipment.

Red
 

Roy G

Roy
Senior User
My shop is a barn. I've tried paste wax, the spray on coatings, the breathable coverings and nothing really keeps the rust away. I put plywood covers on al my tables to keep the rust off. This works.

Roy G
 

DavidS

David
User
I read the same article in Fine Woodworking and have been using CRC 3-36, which is a multi-purpose lubricant and corrosion inhibitor. I do not use paste wax afterwards, and it works really well. By the way, I live in the mountains of NC so I heat in the winter for about three months, but I do not cool my shop in the summer. Previously, I had a dehumidifier; however, it broke, and this last summer, I just kept the doors and windows closed and used the CRC 3-36 without any problems.

I buy the CRC 3036 from Amazon for about $5 per can. Here's the link if you are interested:

http://www.amazon.com/dp/B00192EX10...UTF8&colid=2RR6IJ975K6D&coliid=I24NYPIR0GX0G1
 

chris_goris

Chris
Senior User
Warm cast iron doesnt condensate, cold does. So if youre going to control temperature, its best to heat to eliminate rust issues.
 

zzdodge

New User
zz
My shop is a barn. I've tried paste wax, the spray on coatings, the breathable coverings and nothing really keeps the rust away. I put plywood covers on al my tables to keep the rust off. This works.

Roy G
I use a melamine covered hardboard (less than $12/4x8 sheet) and make a frame out of dimensional lumber. Urethane the frame. The white melamine doubles as a whiteboard, and I can draw while it is horizontal on the table, and hang it or lean it against a wall when the equipment is in use. White keeps the shop brighter. A microfiber rag picks up sawdust so as to not clog the marker, and doubles as an eraser.
 

BKind2Anmls

New User
Susan
Roy, I always heard covering the tool would trap the moisture. does it keep condensation off of your tools?
 

chris_goris

Chris
Senior User
My shop is a barn. I've tried paste wax, the spray on coatings, the breathable coverings and nothing really keeps the rust away. I put plywood covers on al my tables to keep the rust off. This works.

Roy G
Anything that doesnt breathe would probably work, Like I said before, its from a rapid temperature swing that you get condensation and if you can keep the warm humid air from reaching the cold cast iron, thats all you need to do. All the waxes and boeshield type products etc arent going to do you any good if you cant. Your cast iron will get wet if this happens.
 

zzdodge

New User
zz
Roy, I always heard covering the tool would trap the moisture. does it keep condensation off of your tools?
I haven't tried it but perhaps a Tyvek cover might work for some tools. It would pass water vapor through, but generally repel moisture from things like wet clothes coming into the shop.

Moisture forms on tools, accelerating rusting, when the tool is at or below the dew point temperature. The room temperature and dew point temperature are the same at 100% relative humidity. If an object is cooler than the dew point, water will form on it.

However rust can actually happen before observable water.

I don't know the best treatment for cast iron in tools. I have been lucky and have conditioned air, and very dry shops. Cooling air dries the air out because the moisture is removed (well some of it) as it passes over the cooler evaporator in the AC unit. Actually, having a lower capacity AC than needed in a shop can be a good thing. It will dry the air out a bit more, cycle less, and tend to take a little less energy than a normally sized AC. It is better to have your shop have it's own AC system, rather than use the "house" system.

Back to rust...the chemical action creating rust will roughly double in activity with every 10F increase in temperature. So a cool shop with non-condensing humidity will not have it's tools rust nearly as fast as a rather warm shop with non-condensing humidity.

Also, another trivia item from experience...a dew point of about 65F feels sticky or damp to most people. Conditioning and other factors may vary that for an individual. So if the shop is 80F and feels dry, chances are your dew point is below 65F. When your tools cool to the dew point, there will be condensation, like dew on the grass as the sun sets.

If you "bag" a tool, do it on a very dry day, and see if you can include some silica gel in the bag, as it will absorb water from the air in the bag. The silica gel can be warmed in an oven, driving the humidity out, periodically.

Sorry about the rambling, but as I mention these things, I realize that keeping iron from rusting in a shop is somewhat non trivial. Dry air and perhaps heat are your friends, but you have to be careful.

Final story. A person I know of put a ventless gas heater in his outbuilding shop, to keep it warm for wintertime work. The problem was that the gas heater gave of water as a combustion byproduct, raising the humidity in the shop, and within a year he had rust problems. Switching to a regular furnace and a forced air system solved the rust accumulation, and dried out the shop. When it was really cold, he ran the ventless heater a little to increase the humidity in the shop, which had the effect of reducing static. It also made it more comfortable when it was real cold outside, because the humid air feels warmer.
 

Tarhead

Mark
Corporate Member
I do 2 things:
Keep the exterior shop doors closed when the outside dew point is higher than the temp of the cast iron.
Use a liberal amount of Bruce's (Junquecol) miracle juice (1/2 block of Gulfwax paraffin) dissolved into ~8oz of Mineral Spirits in a spray bottle), allow to dry and buff with a shop towel.
 
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