POR or Glass First ?

[somolovitch3]

Does one use POR-15 first or does one fiberglass to clean metal then POR ?

[burnt_servo]

i'd use the fiberglass to bare metal   .

[macka]

POR first, make sure the bare metal is clean, use the POR metal prep. Once that is done, then glass it.

[clbanman]

Fibreglass first (to rust free metal).  If you glass over the POR, your repair will be only as strong as the bond between fibreglass and the POR.  The bond between fibreglass and metal is stronger.

[burnt_servo]

if you believe por's propaganda  , they will tell you to always put por on metal first , then everything else on top of the por ......

this spring i built a shaker to seperate gold out of gravel concentrates , and i preped and painted the whole thing in por 15 .

everything was done properly , and about 30% of the por has flaked / peeled off of the steel .

so take what the comapany tells you about their product with a bag of salt

[macka]

Fibreglass first (to rust free metal).  If you glass over the POR, your repair will be only as strong as the bond between fibreglass and the POR.  The bond between fibreglass and metal is stronger.

If you glass over the metal first, there is no real reason to buy the POR15. The resin is airtight. POR15 is for resto work.

[Peter]

Profesionals don't use Por..even though the resin will provide an air tight seal, the metal must be absolutely clean...if not, in the near future it will peel off...better still, ..zinc over rust free metal for long lasting results

[macka]

The trick to getting metal clean is using your noggin and getting both sides taken down to bare metal, then making sure you have cleaned the surfaces and they are contaminant free by using methylated spirits and not touching the surface with anything contaminated after it is cleaned. The resin is then applied in a glaze coat, then while it is still slightly tacky you finish layering on your glass.

[Syncroincity]

Yeah, my experience with POR is that anything you apply on top of it, even their tie-coat, will come off eventually. Maybe roughing it with fine sandpaper first would help?

On the other hand, using POR in conjunction with the fiberglass mat yields a nice, strong patch, you can skip the resin entirely. You can also use it to fab parts... using black POR and 'glass mat I've made replicas of all the cardboard radiator baffles on my van that had rotted away. AND... it looks like carbon fiber when it cures.