POR-15 paint Tchernobyl...

[Surcouf]

So... one of the main reason for me to pull my A4 out ofmy C27 is to stop the rust, and paint the block. I have not painted the block itself yet, but already done the head, the manifold, the flywheel housing etc...
Sequence applied was: multiple cleaning / de-greasing, then rust chipping and brushing, then POR de-greaser, then POR metal prep, then 2 coats of POR-15 trying to do everything as per the book. I was then planning to add a coat of POR heavy primer, before spraying the final MM paint.

all my parts such as head, manifold etc.. were already free of paint (due to corrosion etc..), and look good. But the oil pan is a catastrophe... the POR-15 paint is flaking out in large pieces (pics to follow).

Any idea why this is going south? what I am doing wrong? Should I removed any trace of old paint? POR FAQ maintains that old paint should not be an issue. My next step is to paint the block, I would like to make sure not to have to do it twice! (even though there is not much paint left on block...)

[Surcouf]

Oil pan nightmare

[ronstory]

From the photo, it still looks like you may have paint residue on the pan.

For POR15, the best thing for it to attach is a clean lightly rusted surface. When I built my factory 5 cobra replica, I got the steel frame unpainted, degreased with a rag and acetone, used the metal prep and then put a yard sprinkler on it and ran it 30 mins a day for a week.

I got a nice light rust coating that the POR15 loved and its been hard as nails for 18 years.

[jcwright]

My experience with POR-15 is similar to Ron's as far as durability and hardness.

Surface preparation was fussy. I see the following instruction from POR in my notes, which makes me wonder if humidity was a factor for you (Surcouf):

"POR-15 is cured and strengthened by exposure to moisture and will dry faster under extreme humidity, but moderate to dry atmospheric conditions are most desirable when applying this product,because extreme humidity may cause an immediate surface cure, trapping carbon dioxide gas below the surface. When this happens, bubbling may occur. Extreme humidity at the time of application may also interfere with proper adhesion of the POR-15 coating to metal because it's almost impossible to keep metal dry under such conditions."

Jack

[Surcouf]

My experience with POR-15 is similar to Ron's as far as durability and hardness.

Surface preparation was fussy. I see the following instruction from POR in my notes, which makes me wonder if humidity was a factor for you (Surcouf):

"POR-15 ......"

Jack

it is a good point and I understand the concept behind. But I have a de-humidifier in my basement, and with the cold temperature there was less than 55% humidity. very very dry. Moreover, I was rinsing the pan with very hot water, until the pan was at the water temperature, to ensure a better drying...

So I guess I am good to strip that paint away.. and start again. I hate paint stripper...
Thank you for your help!

[ronstory]

I would recommend you just take the pan to your shop and hot tank it. In your original pic, I believe that showed left-over bronze paint under the POR-15. POR wants a clean metal surface for attachment, ideally a bit of surface rust.

Just have them clean and strip down to bare metal, then spray metal prep or lots of vinegar let dry ... rinse with water... wait a day or so and then paint again.

It will stick like thinset.