Hi,

I am looking for a better understanding and comments of corrosion on cores. Background: we have cylindrical cores that due to size and geometry tolerances, we don't make from stainless. Instead we use tool steel and nickel plate them. Recently, we have experienced corrosion on one month old tool. It is sufficient to penetrate and lift up the plating. The water is treated with corrosion inhibitors, ph is running 8.6 and water temperature is 180 F. Any thoughts and ideas would be appreciated.

Thanks,

Dan Steerman

Dan, My first question would be why you chose to use a Nickel Plate for your cores ? Also, which Nickel process was used ? I can think of a number of Hardcoat applications that would serve you better. Are you looking to reduce/eliminate corrosion in your cooling channels ? If so, the deposition for electroplating is not very effective in deep blind holes that are typical for cooling channels. Although you have a water temperature of 180 F, the tool steel would probably be much higher----and the thermal cycles can be detrimental to the bond of the Nickel. Since you are using treated water and your Ph is understood, I would eliminate the Nickel Plate and just have bare steel. I have been to many countries that have problems with corrosion and various calcium/mineral buildups in the water channels and for those regions it is typical to establish a preventive maintenance schedule to clean the channels. I have seen mineral buildups that are > 50% of the channel flow area !!! I hope my comments help.

Tool steel for construction of core & cavity inserts are normal. If there are corrosion mean there are water leakage from cooling lines. At 180F condensation should not be a problem. A good practice is to use compress air to purge all cooling holes fee of water and apply antirust on mold surfaces before storage.

if you are warming the mold to 180 degrees F. Use a dedicated hold heater for this mold and use heat circulating fluid ( oil) to warm the mold.

dear Mark , Dan talking abt corrosion on core & cavity of moulds , not in the channels,
here Chiu is right , this should solve the problem , if done properly.

Thanks! Let me explain more. These cores are directly cooled by exposing them to the cooling channels using o-rings above n below. Wish I could post picture. There are no leaks and the corrosion is limited to the area exposed to cooling water but it is approaching o-ring groves. I don't know plating process but cores were plated before finish grinding. No scratches were present in affected area.

Once plate and corrosion makes to o-ring channels, tool will leak and cores will have to be replaced. We have discussed about using heat exchange type thermolater. But oil really was on the list....50% glycol was discussed. But I couldn't discuss interms of corrosion as I have only seen it used to avoid deposits n scales.

Let me mention the plating is limited to the cooling area, o-ring channels, not the rest of the core that makes the part surface.

Dan, I must ask, What material are your "O" Rings ? High Temp ? Viton ? Perhaps they are not capable of the Core/Cavity Temperatures. Also, Is there a reason your tool design uses "O" Rings for the water fittings ? How about regular pipe threads with High Temp Tape and use Quick Connect Fittings. The Nickel Plating seems to be part of your problem and I've never seen it used in this type of application.