Corrosion due to high humidity

[MarcelNL]

Our heat pump works great to keep the house cool in Summer yet it also increases the relative humidity inside....

I just noticed some of my knives are corroding and I wonder how best to remove that light layer of corrosion and how best to prevent it? (short of a whole house de humidifyer)

(humidity is at around 75% inside, 55% outside)

 

[HumbleHomeCook]

I'd start with a water/baking soda paste and your finger.

For prevention, a mineral oil/bees wax 4:1ish blend and very light wipe down should go a long way. You could just do straight mineral oil first to see how it goes. Wipe on, wipe off, monitor. Just a little easier to put straight into service than the wax combo which will take a slight bit more wiping off.

 

[JBroida]

flitz, simichrome, or similar metal polish... better than baking soda, BKF, etc... and leaves a protective coating that will keep it from rusting in storage. Just wash it off well before using again.

 

[esoo]

Our heat pump works great to keep the house cool in Summer yet it also increases the relative humidity inside....

I just noticed some of my knives are corroding and I wonder how best to remove that light layer of corrosion and how best to prevent it? (short of a whole house de humidifyer)

(humidity is at around 75% inside, 55% outside)

Is this a whole house heat pump or something different? I would've expected the heat pump to run like an AC unit in the summer and that, at least on my home AC unit, works like a dehumidifier. In fact, I can set on my smart thermostat to have it fire up the AC to control my house humidity.

 

[MarcelNL]

Is this a whole house heat pump or something different? I would've expected the heat pump to run like an AC unit in the summer and that, at least on my home AC unit, works like a dehumidifier. In fact, I can set on my smart thermostat to have it fire up the AC to control my house humidity.

the heat pump is connected to a geothermal well, which in winter allows drawing energy from it and in summer allows having colder water flow through the floor heating system.
It will monitor relative humidity and dew point etc to avoid floors from getting wet but it cannot dehumidify.

AC uses far more energy per unit of heat produced than this system, the cooling function is a bonus but as we now see it has some downsides...


(still, the other option is not cooling which would mean 90+ F in the house for weeks...it now stays cool at around 70 F at very low energy cost)

 

[MarcelNL]

I tried a miracle sponge, and it gets a bit off, will try baking soda next and then some polish followed by a good coat of beeswax and oil!

I could try Dammar.....(resin dissolved in natural turpentine) (smells great but likely not food safe)

 

[HumbleHomeCook]

Let us know how things go and what you ultimately end up doing on both fronts.

 

[spaceconvoy]

75%?! I'm in Florida and that sounds crazy to me. I'd be worried about how that amount of moisture affects much more than just your knives

 

[stringer]

I keep a lot of knives in my basement where it is very damp. A healthy patina helps a lot. Your worst case scenario is going to be BNIB type knives. They are going to be much more susceptible to environment induced corrosion. 75% is awful high though. I have a whole house dehumidifier running in the basement to keep it stable at about 60% and it is pretty wet down there sometimes. I would be worried about mold and mildew and roaches and shorted electronics in that kind of environment.

 

[Jovidah]

Open a window and suffer like the rest of us plebs?

 

[esoo]

the heat pump is connected to a geothermal well, which in winter allows drawing energy from it and in summer allows having colder water flow through the floor heating system.
It will monitor relative humidity and dew point etc to avoid floors from getting wet but it cannot dehumidify.

AC uses far more energy per unit of heat produced than this system, the cooling function is a bonus but as we now see it has some downsides...


(still, the other option is not cooling which would mean 90+ F in the house for weeks...it now stays cool at around 70 F at very low energy cost)

Ahh. Geothermal system

Heat pump to me means something different. Generally in this area it is referred to as systems which would run like AC but run both ways (heating and cooling)

 

[superworrier]

Ahh. Geothermal system

Heat pump to me means something different. Generally in this area it is referred to as systems which would run like AC but run both ways (heating and cooling)

I think those are both heat pumps, just geothermal source vs air source.

 

[esoo]

I think those are both heat pumps, just geothermal source vs air source.

Yeah, I looked that up. But in this area we call one heat pump and the other geothermal.

 

[Lars]

Read the title and assumed one of your audio connections had failed

 

[MarcelNL]

Read the title and assumed one of your audio connections had failed

Just the wifi today ;-)

but that was due to me tinkering with the router settings...

 

[MarcelNL]

Open a window and suffer like the rest of us plebs?

it's approx. 80% outside at the moment, so I'm not sure if that helps an awful lot...

The cooling kindof concentrates the air inside making the moisture build up, luckily its not weeks in a row but I still would like to find a cure that does not involve much energy like AC.

 

[esoo]

Yeah, cooling air drives up the relative humidity.

I went back and looked at my thermostat logs. Last week out daytime was 55% but that rose to 95% as the temperature dropped overnight.

 

[M1k3]

it's approx. 80% outside at the moment, so I'm not sure if that helps an awful lot...

The cooling kindof concentrates the air inside making the moisture build up, luckily its not weeks in a row but I still would like to find a cure that does not involve much energy like AC.

Dehumidifier?

 

[WildBoar]

Dehumidifier?

Dehumidifier??? I hardly know her!

 

[jjlotti]

Maybe a service check. I have had geothermal heating and cooling (compressor in conditioned crawl space) for the last five years. My humidity is stable around 50%. Cooling is achieved by pulling moisture out of the air like any a. c. or heat pump unit( hence the drain). You may very well need a inline dehumidifier. I imagine yours knives are not the only things degrading. I once stayed in a place in Mexico that had what they called "swamp cooling" which was miserable. Cool for sure but so humid felt like when your sheets are not quite dry all the time.

 

[Dan-]

Hey @esoo, are your emitters radiators or in-floor? A typical water source heat pump (aka geothermal) with forced air isn’t much different from an air source heat pump, which does dehumidify.

 

[esoo]

Hey @esoo, are your emitters radiators or in-floor? A typical water source heat pump (aka geothermal) with forced air isn’t much different from an air source heat pump, which does dehumidify.

I'm air source. Wish I was geothermal but not going to redo everything for that in this house.

 

[Dan-]

Apparently halfway down I forgot who OP was. Same question @MarcelNL

 

[Veitchii]

Our heat pump works great to keep the house cool in Summer yet it also increases the relative humidity inside....

I just noticed some of my knives are corroding and I wonder how best to remove that light layer of corrosion and how best to prevent it? (short of a whole house de humidifyer)

(humidity is at around 75% inside, 55% outside)

Violinists occasionally use dehumidifying packs (just silica desiccant) inside their instrument cases to regulate moisture. Putting one in a case with your knives might be worth a shot, but that's just an idea and I haven't tried it myself.

 

[mengwong]

What does this VCI experiment tell us? Nothing. Because there was no control.

 

[MarcelNL]

Apparently halfway down I forgot who OP was. Same question @MarcelNL

in floor, closed loop water circulation based heating/cooling. The system is brand new and works just fine (after the water return temp sensor was replaced that made it heat up to 24'C with the set temp at 21'C in March)

It's not a fault i nthe system but physics driven, VCI paper may be worthwile for the knives but indeed an inline dehumidifier in the ventilation system may be needed.

Silica gel is likely not enough, and as mentioned by others, other stuff will corrode too.

Less cooling is also not hacking it, a few degrees warmer the same thing happens when moist warm air is cooled inside. Suffering 30'C outside and inside gets old real quick, been there done that long eough in our previous home. With the current building code insulation the houses are pretty much a thermos flask, once heat gets in it takes forever to get out.

I'm reading up and found numerous folks reporting the same issue, some are building a whole house dehumidifier to place inline with the ventilation system, which sounds tempting. My problem is that the room with the heatpump and ventilation does not have much free space left....it's like an engine room.

 

[mengwong]

some are building a whole house dehumidifier to place inline with the ventilation system

This strikes me as a complicated way to synthesize a conventional central air conditioning system…?

Which, to be fair, has its downsides too. When it looks like this outside

It looks like this inside

 

[Jovidah]

Less cooling is also not hacking it, a few degrees warmer the same thing happens when moist warm air is cooled inside. Suffering 30'C outside and inside gets old real quick, been there done that long eough in our previous home. With the current building code insulation the houses are pretty much a thermos flask, once heat gets in it takes forever to get out.

My appartment is also fairly new and it has the same issue; once it gets hot it's hard to cool down. The trick is to ventilate as much as you can when the outside air is colder (usually 10-12 pm until about 9-10 am), and then keep things closed during the daytime (windows + curtains).
Since you're letting in colder air that should also make the moisture issue less problematic.
With all of these newer buildings, even if they have a ventilation system that's supposed to be sufficient on paper, I've found that proper ventilation through the windows is still a must to retain a comfortable environment.

 

[MarcelNL]

My appartment is also fairly new and it has the same issue; once it gets hot it's hard to cool down. The trick is to ventilate as much as you can when the outside air is colder (usually 10-12 pm until about 9-10 am), and then keep things closed during the daytime (windows + curtains).
Since you're letting in colder air that should also make the moisture issue less problematic.
With all of these newer buildings, even if they have a ventilation system that's supposed to be sufficient on paper, I've found that proper ventilation through the windows is still a must to retain a comfortable environment.

that is correct for a home without geothermal heating, here the ventialtion system has a bypass to allow cool air getting in during summer and ventialtion works really well.

Regardless of how much I ventilate at night if we start cooling the humidity goes up.

This strikes me as a complicated way to synthesize a conventional central air conditioning system…?

Which, to be fair, has its downsides too. When it looks like this outside
View attachment 267993
It looks like this inside
View attachment 267992

it is different as it is only in use when inside humidity is high and floor cooling is active (managed by outside and inside temp difference over x hours with y degrees gradiant and dewpoint z) , the air being blown into the house would be/should be drier than currently is the case and not that much colder.

 

[HumbleHomeCook]

Sooooo... How's the rust removal going?