Paint for microwave

[ss]

I have a couple of rust spots inside microwave, 3 years old so should last a bit more. Any ideas on what type of paint I could use to touch it up. Rust about 3 x 1 cms size.

[newshound]

Why?

[ss]

Because SHE will buy another microwave if I dont get rid of the rust! It works perfectly well.

[Graham.]

You can buy special microwave paint, Google for it. It's probably the same as car paint or something, who knows?

The best advice I can give is when you replace your microwave, do what I did and choose one with a stainless steel cooking cavity.

[Sam Jackson]

What is used on cars should be fine.

[Brian Gaff]

Unfortunately from my experience, once you can see rust inside it the rust has spread under the existing paint and although the machine will probably go on for ages, it looks naff and paint bits come off as you clean it. Much like other things you would need to take it apart and treat all the rusty bits and remove the loose paint. The paint I understand is some king of stove enamel put on when the parts were manufactured, so really you might end up with a lot of expense and decide to get a new one or use it as is until it starts to give issues. My last one went on the bend of the door as it was bottom hinged and it started to leak microwaves there. It was a Swedish made Philips as I recall Just crap applied paint. Brian

[Brian Gaff]

It does beg the question what has been used to clean it of course and whether it was left wet with a corrosive substance on it. Brian

[Brian Gaff]

Chuckle however not all stainless steel is also going to be rust proof. Most these days are some kind of alloy.

I guess if somebody wanted to experiment, a bit of a sand down and a touch up might work, but not for long.

Brian

[charles]

All steels are alloys: Iron and other things

[Tim Streater]

I would have thought all stainless steel is going to be rustproof. That's rather the point, isn't it?

[Chris Green]

Yes. However the level of rustproofness will depend on the particular alloy. The two common stainless steel 'types' are A2 and A4. A2 is general purpose and is fine for most inland domestic use, A4 is more rust resistant and is aimed at marine use and such.

Any stainless will rust in certain situations, in particular it will often rust when touching rusting non-stainless steel.

[Martin Brown]

Notably stainless if it contains more than a certain percentage of chromium. It was invented discovered more than once but it was Brearley in Sheffield who is usually credited. He was looking for improved gun barrels. German inventors had some prior art with a 21% Cr 7% Ni steel.

Slightly longer and more detailed version here

Basically he accidentally made a batch he couldn't etch!

[dennis]

I think the only stainless that rusts in common use is for saucepans so that they work on induction hobs. It appears its quite expensive to make rust proof and magnetic. Some better pans have three layers so the magnetic stainless is wrapped in rust proof stainless.

The alloy pans I have have a steel base fitted but they don't work as well as the three layer stainless ones do. You can boil water quicker in the better ones so there must be something restricting the power input on the alloy pans.

[Andrew Gabriel]

A rusted microwave (inside the oven, or outside) will usually be a PAT test failure, because of the possibility of microwave leakage. If you can clean up the metal sufficiently to show it's not rusted through and then protect it again, you'll probably be OK, but that's never worth doing commercially. If the rust is at a seam, then forget about repairing it, because you will never be able to make the seal sufficiently electrically conducting again to prevent leakage.

[Andrew Gabriel]

Also, it is only stainless in the presence of oxygen, to form the chromium oxide protective layer. Without that, the iron in it will corrode. Things that strip the chromium oxide protective layer will also allow it to corrode.

[Andrew Gabriel]

Making pan bases is an interesting challenge.

Stainless steel is a nice finish, but it's a poor heat conductor which can lead to uneven heating and hot spots with many types of hob, and it doesn't work well (or in some cases, at all) with induction hobs.

Aluminium is a very good heat conductor for even heat with no hot spots, but is not a good surface finish (unless teflon coated or similar), and won't work with induction hobs.

Copper - same as for aluminium, but no use as a surface finish.

Iron/steel is good for picking up heat from induction hobs, but is not a good heat conductor, so it needs a thick/heavy base or you will get hot spots, and not good as a finish so has to be enamaled.

Since none of them is good in all cases, good pans are forced to have multi-layer bases - typically stainless steel inside surface (or teflon coated aluminium), with an aluminium or copper heat spreader on the base, and for induction hobs, a steal layer to pick up the induction heating. The layers, which expand differently when heated, need to be well bonded to conduct heat through. (They do occasionally come apart.)

[tabbypurr]

Any solvent based metal paint, even old humbrol enamels.

NT

[Max Demian]

I leave the door open to dry out after use.

[alan_m]

+1

When looking at the models with stainless steel inners also select the one with the fewest number of 'ventilation' holes - some seem to have fully perforated panels on all sides as well as the top while others have small areas of perforations making cleaning less of a chore.

And if its microwave only, consider buying one of those large microwave splash guards - when something explodes it mainly only covers the inside of the guard which can easily be washed.

[newshound]

My sympathies! Evidently it's not stainless, then? If it was an expensive one, it might be worth going back to the supplier. I recently had a good result from Amazon when a TV failed at 5 years, apparently the "accepted" life for TV's is 6 years, and after one phone call to them and another to a service centre, and then a firmly worded (but not rude or aggressive) email they gave me something like a 15% discount on a new one.