December 2nd, 2020

Tick, tock… time is not on your side. There is a limit to how long a mold can sit unattended, even with the best rust preventive.

For example, let’s talk about THAT mold – the one that sits on the shelf for several months, or even years. Then the customer calls, the order comes in, and you pull the mold on schedule to start making parts.

The mold is cracked open and you see it: rust. What might have been a quick prep job is now a mold repair project. So, what happened?

You Are Not Alone

The Slide team gets many phone calls on the topic of rust. One caller wanted to know why molds coated with a five-year rust preventive showed signs of rust after a period of only several months. During the course of a short discussion, we learned they were storing the molds outside. Rust preventives are not formulated to handle an outdoor environment.

Set Your Alarm, Check Your Mold

There are a couple of different timelines, depending on your molding environment, for inspecting and protecting your mold.

1) If you are storing a mold longer than 6 months
The American Society for Testing and Materials (ASTM) designates long-term rust preventive, like Slide No Rust, as being effective for up to five years of indoor storage. If you are storing a mold longer than six months, we recommend that the entire mold block (cavity as well as mold base) be protected with an oil-based rust preventive.

Set an alarm for 12 months out
It is also best practice to crack open and inspect any mold stored for longer than 12 months, looking for any signs of corrosion. You should reapply rust preventive product following these inspections to ensure all critical surfaces are protected.

2) Molding gas-emitting resins?
Has your mold been running PVC or any other gas-emitting resin? Be sure to use a rust preventive with protection against not only corrosion due to moisture, but also oxidation caused by the acidic vapors released by these resins. This would be a rust preventive like Slide’s Acid Vapor Neutralizer.

Set an alarm for 30 days out
To ensure your mold has continuous protection you should reapply the rust preventive that protects against acidic vapors every 30 days to ensure that the acids present in the area around the mold continue to be neutralized.

More Tips to Protect your Mold

As the mold is cooling, apply rust preventive to the mold cavity, the plates and mold base to help prevent condensation from causing rust and oxidation. This is a “dirty” step since the hot mold will likely cause the oils in a rust preventive to liquefy and run. It still protects the mold until it is cool enough to pull and take it to the tool room to break it down. Slide’s Mold Shield is ideal for short-term protection. If you need a food-grade formulation or you are molding medical parts, use Slide’s White Rhino rust preventive.

Now that you are in the tool room, break down the entire mold system to look for gas buildup, color stains, water stains, resinous deposits and any other contamination that might have built up on the mold unit during the production run. Use a mold cleaner and/or a mold polish to remove these contaminants and leave you with a clean mold.

Now follow the rust preventive guidelines mentioned earlier, based on your storage timeline and indoor environment, and you can be assured your mold will be ready to perform with your next order.


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