Letter 24113

Chrome plated parts have pin hole problem  

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My company is mainly involved in the injection of plastic parts for cars.
Recently, we are facing problems with our new chrome parts, the main problem we face is the surface of the parts have pin holes problem(very small holes that are hard to see until you chrome it).

We have already tried using a dehumidifier while producing the plastic parts, sanded the surface of the mold(doubt it is caused by the mold since the pin hole runs around the part), but we still couldn't solve the pin hole problem.

Does anyone here have any advise?
Secondly, I would like to know what type of mold material should I used when making the mold?
And typically the hardness should be in what range?

Thanks in advance.

Mew, Yu Tsing
Automotive - Shah Alam, Selangor, Malaysia

To sand blast the mold is completely wrong way. The molds for injection of plastic parts that are to be chrome plated must have the very best mirror finish (preferably they would also have to be plated to avoid rust and reduce scratches). If the pinholes are present before the plating, then something is wrong with your injection parameters or resin. You didn't mention what type of plastic you run. If it is ABS, it has to be purchased as "plating grade". This plastic was designed for plating and for its preparation it will develop microscopic pinholes (locks). Proper plating procedure will level (fill) these microholes and produce a mirror finish.

Guillermo Marrufo
Monterrey, NL, Mexico