How long should I keep my recently vapour blasted steel engine components before getting a primer coat down

Probably leaving it a little late in the year for painting parts of my 5”G locomotive I have had some of the smaller items, platforms pieces and the like vapour blasted by the local shot blasting company and they are now currently boxed up in the workshop pending a change in the weather. Not too concerned about the all copper/brass components, the main concern of course being incipient rusting before able to apply a coat of prime. Current thinking is to keep the steel pieces covered up in the box in the relatively cold but dry workshop to minimise any chance of condensation. That is how things have remained for the last two weeks but I have found myself wondering just how much time I have got before the dreaded signs of rusting being to appear. Any thoughts and views and details of firsthand experience on such matters would much appreciated.

I would paint them as soon as possible.

As soon as it has been cleaned, steel begins to corrode. Any humidity provides all it needs to rust. If you havent stored it in VCI paper or sealed bags with dessicant pouches then paint it now.

I was told by my shotblaster to prime the parts immediately.

Chris Gunn

A sudden change of weather from cold to warm and wet will see condensation wreak havoc on bare steel. Handling with bare hands soon puts rusty fingerprints on blasted clean steel. A coat of primer will offer some protection but even primed jobs seem to succumb eventually. If you don’t mind having to thoroughly degrease the jobs then a protective oil coating could be used until a full paint system can be applied.

Mike

Vapour blasting removes all traces of surface residue leaving bare metal exposed to the elements. Surfaces will oxidise quickly dependant on what they are exposed to, even some peoples finger oils can adversely affect metals. Applying anti oxidant oils is recommended for long term, 12 month max, storage. I would refinish as soon as possible otherwise you may have wasted time and money having it done before your ready to finish.

Primer is by it's nature porous so that the topcoat bonds properly, so the water can get through it.

Any soldering work done near the bare steel will also cause rust.

I have noticed that panels left with only a primer coat on cars do start rusting after some weather exposure so being porous would tally with that observation

Mike

I've not tried it, but storing inside a vacuum clothes storage bag should buy time. This example is from Argos, many others available.

They work by removing air with a household vacuum cleaner hose. Pumping the bag out would get rid of most of the Oxygen and moisture in air that causes rust. The metal is still vulnerable, but problem deferred.

Dave

Can you put the steel parts in the airing cupboard indoors?

When I was a kid I kept the newly rebored and cleaned V6 engine block from my Zodiac in my bedroom, until I had saved up enough to reassemble and reinstall the engine !

Edited By John Doe 2 on 06/12/2022 10:36:04

+1 on what Baz and others have said - I've seen rust starting within minutes on freshly blasted parts.

Rob

too late now should have painted it before you took it home will need doing again

If any signs of rusting appear I would be inclined to use a rust treatment to neutralise it before painting. I have used rust treatment rather than keep discing until rust pitting is removed and most of the steel. Obviously you won’t have severe rust to deal with but neutralising any rust bloom could be useful.

Mike

one of my friends was a commercial shotblaster and I used to get my old stationary engine parts ,ie some steel (fuel tanks) and a lot of cast iron,blasted, when blasted I took the parts home and and painted immediately with a thinned down coat of red oxide and when dry a thicker normal coat,the friends work was mainly for commercial vehicles ie water pumps,steering boxes and these ere just sprayed matt black as corrosion protection was not really required as English lorries threw out enough oil to stop rusting. The thin coat ensured that any pits were coated and the thick coat gave corrosion protection. With bright loco parts why not store them in the airing cupboard and paint them indoors, utility room is ideal as the floor covering is tiles so there is very little dust,I once got the engine bed of a 7 Hp cCossley into our hallway,it sat on a sheet of hardboard over the carpet but this is not ideal as dust from the carpet rises as you move around painting and ruins the paint finish, I also keep the the high tension magnetos in the airing cupboard,one spare has been there over 40 years,I have tolerant wife as she also buys her own engines though i get the job of restoring them.

I have watched blasted parts go rusty in 20 mins, so as others have said, it's toooo late ! Noel

I sprayed a motorcycle petrol tank black in my mums kitchen. It was not a good idea, my makeshift booth did little to contain the black dust cloud that covered every surface, even the sugar bowl had a layer on the sugar.

Mike

In my youth I and many others did car bodywork touch ups and rattle can resprays. It used to amuse me how many seemed to leave them at the grey / red primer stage which soon showed evidence of rust. Not sure why, perhaps time or waiting for a better finish from someone else or availability of the matching top coat colour. Never seem to see this now.

Well, for what it is worth, I have spent the day spray coating the parts with acid primer and they are now tucked up in doors where they can hardened off overnight and there remain until the better weather comes. Note to self: On any future work the primer should be applied on the same day as collection from the shot blasters.

Watched a Car SOS recently, they had a bodyshell shot blasted and at the same time a length of steel which was chucked outside, covered in rust in under two hours.

Bill D.

Why is it late in the year to paint something? I've just been in my unheated garage to check the Union T&C Grinder cabinet I sprayed Sunday afternoon and it's as expected, just fine, I'm genuinely confused why you shouldn't paint at this time of the year?