Stainless steel and cast iron rust

[Shawn_Laughlin]

I’m marking stainless telescopic way covers for my lathe and the first section, the stationary one,at the headstock,the cover sits on top of the ways and noticed when I removed it there was some surface rust which made me sick to my stomach when I seen it.

I’m pretty good about keeping the machine oiled down so it’s left me wondering it has something to do with the stainless steel being in contact with the cast iron ways, sort of like galvanic corrosion.

So my question is will doesn’t stainless steel cause cast iron to rust or corrode quicker?

 

[Alexander McGilton]

Are you using water based coolant, especially some that has expired? Im thinking more that stainless steel has trapped moisture.

 

[savarin]

Some stainless will show signs of rust. I have some stainless steel cutlery that always show it when washed in the dishwasher.
It does rub off with a vigorous polish.
As to why I always put it down to the very high Ph of the dishwasher soap.

 

[RJSakowski]

The OP was referring to rust pn the cast iron in contact with the stainless. Stainless and iron/steel does create a galvanic couple. I had a rather scary personal experience with that phenomenon when the stainless steel braid covering a flexible brake line corroded the steel line connected to it. The steel was corroded to a near perfect bevel and catastrophically failed during an emergency braking. Fortunately, the emergency was a rabbit in the roadway and not a child.

The combination of the stainless, the steel, and road salt formed the fatal mix but any conductive solution in contact with the galvanic couple can cause this corrosion.

 

[Shawn_Laughlin]

I know some stainless steel grades will rust if heated to high and if hydrochloride acid is near it and any grade can rust if say you use a carbon steel wire wheel on it to clean or even if you scratch it with a piece of black iron. I’ve been a welder/fabricator for all my working life so I have knowledge about but what I’m worried about is will the stainless cause the cast iron to corrode.

I would be absolutely sick if I killed my ways bc of a stupid mistake, when I all I was trying to do was keep chips of them.

I am not using any kind of water soluble/based oils, only way oils and my garage is climate controlled so it stays dry. While I know a little, I’m not very knowledgeable on galvanic corrosion outside of using sacrificial anodes on boats, and I searched the net but couldn’t find much so I figured someone on here would know? Maybe I just forgot to put all after wiping them but I’ve done that before and didn’t see rust form.

 

[Winegrower]

I notice a dramatic difference in the quality of cast iron in various equipment. I’ve purchased new a Powermatic 2000 tablesaw, a Powermatic 8” helical head jointer and a Powermatic drill press. At the same time, got a new Laguna 1412 bandsaw and a Skil 12” miter saw. I have a used Bridgeport clone and used Takisawa metal lathe.

Regarding rust, and all in the same environment, an unheated shop in Northern California, and after paste waxing, Boeshield, etc., the table saw does ok, the jointer is horrible, the drill press is marginal, the bandsaw like the drill press, and the Skil saw looks like new. It’s aluminum. The mill and lathe seem to stay oily enough there are no major issues. So the woodworking tools are the most sensitive.

I am no metallurgist, but is there no alloying additive to cast iron that can make it more rustproof? These tools were all perfect when they arrived.

 

[whitmore]

I’m marking stainless telescopic way covers for my lathe and the first section, the stationary one,at the headstock,the cover sits on top of the ways and noticed when I removed it there was some surface rust which made me sick to my stomach when I seen it.

Cast iron is heterogeneous; only some grains or boundaries are rust-prone, so (aside from a bit of etch) your iron is
undoubtedly still good, it hasn't changed its level surface, just grown a few pits. The rust can be polished away
without abrading the intact metal. To be safer in future, you might want to passivate the stainless to build up an
oxide layer. I'm told citric acid works for this, and I've used dilute nitric (in a lab environment, we just had lots of it
around). You don't SEE the oxide layer on stainless (chromium oxide), but it's a barrier to electrolytic corrosion.

 

[RobertB]

So the woodworking tools are the most sensitive.

That is always the issue with woodworking tools. As you have seen with your lathe and mill, plenty of oil does a pretty good job of rust prevention but you can't use anything on the ww tools that might contaminate the wood. I live in coastal south Florida, so not only is the humidity extremely high but there is also salt in the air. Hands down the best thing I have found for my ww tools is Collinite insulator wax, which for me far outlasts paste wax. Once yearly application to my table saw and jointer and they have been rust free for close to 20 years here now.

 

[C-Bag]

That is always the issue with woodworking tools. As you have seen with your lathe and mill, plenty of oil does a pretty good job of rust prevention but you can't use anything on the ww tools that might contaminate the wood. I live in coastal south Florida, so not only is the humidity extremely high but there is also salt in the air. Hands down the best thing I have found for my ww tools is Collinite insulator wax, which for me far outlasts paste wax. Once yearly application to my table saw and jointer and they have been rust free for close to 20 years here now.

Crazy I've never heard of Collinite insulator wax. I'm on the coast of CA and keeping things from rusting is a battle. Fluidfilm works good for my machine tools but the tablesaw and my bandsaw I've tried paste wax on with not so great success. Got me a bottle of the 845 IW and give it a try. Sounds like it would be great for the cars as they stay outside too. Thanks for the tip!

 

[Janderso]

Thank you whitmore,
I was taught stainless does in fact rust but it’s chromium oxide and does not appear to corrode.
You confirmed my thoughts.
It’s amazing how cast iron cleans up. It can appear to be a lost cause but with some rust remover and a little elbow grease, good as new.