Can Security Magnets Cause Blistering Paint?

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M

MacInAction

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I've now seen two metal front doors that have large, growing blisters of paint, both of which had security magnets drilled into them for the home security system. Can the magnets cause a chemical reaction that causes the paint to blister?

I tried to help my neighbor a few years ago to repair the blisters. The blistered areas were sanded to the metal, and painted with one of the major brands that was listed as rusty metal primer. To my surprise, the rust began to reappear as the paint was drying! The job failed, and my neighbor mentioned that the security system was installed a few months before the blisters appeared. Could there be a connection?

I was recently asked to repaint a door for someone in another home that had the same occurrence of random blisters. This door also had an alarm system with a magnet drilled into the door.
 
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If there is a cause, it must be condensation, not the magnets ... This is not a "weird science" moment. :D
 
OP,
As CMV noted, there is a cause or causes but the magnets are not one of them. Incorrect product selection and/or application or poor surface preparation are more likely the cause.
 
when you drill through the rust protective layers to install a screw, you've now exposed bare metal to the elements. Over time, it will begin to rust. From there it's all downhill.
The magnet itself is not the cause, just the installation of it.
Likewise for a door knocker.
 
What would cause the rust to appear moments after paint application? These new rust spots appeared almost immediately, and they grew as we watched. The metal was sanded until it was bare. I assume the 'rusty metal primer' I purchased from the big box store must be the culprit?

I've never seen rust grow before my eyes, and it always baffled me as to how that can happen.
 
It doesn't sound like rust, but more of a reaction to contaminates on the metal. Oil, dirt will cause blisters. What measures did you take to prep the surface? Are you using compatible primer and topcoat?
 
The door is probably painted with latex paint. The spray primer is solvent based. The "blisters" you see are the reaction of the latex paint to the solvent. Yes, you got to bare metal but the perimeter still has latex paint and I would bet the reaction is there, not on the bare metal.
 
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