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Roto mould - avoid rust

Roto mould - avoid rust

Roto mould - avoid rust


I am working at roto moulding industry.
We sometimes counter an issue where the mould is being rust. Although they are thoroughly cleaned prior to use (or oven in), moulded parts have marks due to rust from mould.

The mould is made of Low Steel Carbon.

To prevent it being rusty, would anti rust spray work? Or is there any better way for prevention?


RE: Roto mould - avoid rust

A couple of thoughts:

Climate control. Ensure low humidity to prevent rust.

Wiping with an oil helps. Is this going to contaminate your product? There are film forming additives that are water based that provide some corrosion protection with less contamination potential.

Gelled calcium sulfonate is an emerging coating technology.

Electroless nickel plating would likely be the most permanent and lowest maintenance solution.

RE: Roto mould - avoid rust

Is this happening while they are in storage or while in use?
If in use, then electroless Ni plating is really the best option.
If mostly this is a storage issue, then you have lots of options.
You can buy oils that are 'rust preventative' often called RP oil as they contain corrosion inhibitors.
Even though I call these oils they come petroleum based, veg oil based, as well as water based.
If that would be too messy there is paper and plastic film that contains vapor phase corrosion inhibitors.
You would wrap the molds with these when stored.
It would greatly help if you could lower the humidity, I know that this may be impossible for you.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

RE: Roto mould - avoid rust


To prevent it being rusty, would anti rust spray work?

Yes, it would prevent rust (probably).

But no matter how thoroughly your production guys claim that they clean the mold before use, they really don't.

So whatever spray you use will contaminate your product.

As TugBoatEng and EdStainless suggests, electroless Ni plate.

If it's not too big, and you could make a sealed storage container then you could blanket it with nitrogen for storage.

RE: Roto mould - avoid rust

Thanks all for the advice.

I have 2 questions regarding electroless Ni Plating.

Will such plating last long on the mould which will be run at 230 deg or similar?

Also, I am not sure if this will create any mould release issue.


RE: Roto mould - avoid rust

The EN should be very durable and slick.
Usually, they put down a very thin Cu flash plate and then the EN.
The EN layer is also fairly thin.
After you don't need much since you are not using it for wear resistance.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

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