Painting stainless steel???

[SiXeVeN]

Another thread got me thinking. I have some stainless steel hardware that has recently been "heavily scratched/etched"

I have thought of having the hardware primed and painted with a 2 part polyurethane marine paint but i'm concerned about crevice corrosion issues as stainless steel needs oxygen exposure to chemically prevent itself from corrosion.

I have two thoughts... 1) The stainless steel will be painted preventing any exposure and thus corrosion as it will be protected from moisture and salt by the paint.

2) The paint will block the necessary oxygen exposure and the stainless will begin to corrode under the paint... leading to failure.

Anyone have any thoughts or successfully painted marine stainless steel without issues???

[mitiempo]

I'd remove it and polish it if possible. Then it pretty much takes care of itself.
Brian

[SiXeVeN]

Removal is almost impossible (riveted, bonded, bolted permanently). Polishing would be a B*TCH as the metal is fairly badly etched by sandblasting. (looks frosted)

If it could be painted... that would be easiest. If it can't then well.... I guess I have some replacing/buffing to do.

[mitiempo]

I read your post on the soda blasting thread and now see your problem more clearly. Painting may be your best option but I'm not experienced enough to say how.
Brian

[sailingdog]

Ummm... you're a bit confused... Stainless steel generally doesn't corrode under paint, since paint bonds so closely to the stainless steel and prevents any corrosion, which requires oxygen exposure, from occurring.

While stainless steel does have issues with crevice corrosion, it doesn't suffer crevice corrosion if properly painted. IIRC, for stainless steel to corrode it has to be deprived of sufficient oxygen to prevent the passivation action of the chromium in the steel alloy from protecting it, but exposed to enough oxygen to convert the iron into iron oxide. Painting prevent any oxygen from getting to it, not a limited amount...which would be a problem.

Originally Posted by SiXeVeN

Another thread got me thinking. I have some stainless steel hardware that has recently been "heavily scratched/etched"

I have thought of having the hardware primed and painted with a 2 part polyurethane marine paint but i'm concerned about crevice corrosion issues as stainless steel needs oxygen exposure to chemically prevent itself from corrosion.

I have two thoughts... 1) The stainless steel will be painted preventing any exposure and thus corrosion as it will be protected from moisture and salt by the paint.

2) The paint will block the necessary oxygen exposure and the stainless will begin to corrode under the paint... leading to failure.

Anyone have any thoughts or successfully painted marine stainless steel without issues???

[SiXeVeN]

Stainless steel generally doesn't corrode under paint

That is encouraging. Although I am confused why there is such a warning about sealing stainless fasteners under fiberglass or sealant. The generally accepted reason is low oxygen tension causing corrosion. However, as you said, you need some oxygen to bond with the iron to make rust. Perhaps it is not that the fastener is deprived of oxygen completely it is that the fiberglass or sealant is not tightly bonded to the metal and thus any penetrating moisture will cause the corrosive effect. Thus a well done paint coat should prevent such issues.

Anyone have real time experience with painted stainless steel?

[sailingdog]

Sealant and fiberglass generally don't bond to the stainless steel to the same degree paint does. Water intrusion beyond a sealant is a pretty common thing on a boat, especially if the part is under cyclic loads. That means that water will get in, but not a constant flow of it... which is ideal conditions for crevice corrosion to set in.

Originally Posted by SiXeVeN

That is encouraging. Although I am confused why there is such a warning about sealing stainless fasteners under fiberglass or sealant. The generally accepted reason is low oxygen tension causing corrosion. However, as you said, you need some oxygen to bond with the iron to make rust. Perhaps it is not that the fastener is deprived of oxygen completely it is that the fiberglass or sealant is not tightly bonded to the metal and thus any penetrating moisture will cause the corrosive effect. Thus a well done paint coat should prevent such issues.

Anyone have real time experience with painted stainless steel?

[tommays]

A cotten wheel and a compound stick will buff it MUCH faster than painting it