Repairing a Bosch microwave oven with a rusty door

I'm ashamed to say that recently I noticed rust developing at the base of the microwave interior glass door panel, and the paint flaking. Cooking items like potatoes releases a lot of moisture , which probably should be wiped away immediately to avoid this, but when you are preparing a meal and everything you forget (or I do at least). The Microwave is a Bosch and has a face plate so it fits into a recess in our fitted kitchen.

I looked into replacing the door but Bosch do not supply this as a spare, not could I find a donor oven online. A whole new oven would be around £300, which seemed a lot for a problem that might be fixable. 

I read online about Rusty Microwave ovens, and advice ranged from "It'll be fine" through to " immediately remove the oven and place in a lead lined container at the bottom of the sea" type of response. Filtering the informed advice from the hysterical took a while. In the USA you can purchase Microwave oven paint, and while I couldnt find  it in my local hardware shops, I did find an ebay seller selling a microwave touch-up kit consisting of a small tin of gloss black paint, emery paper , brushes and a stirrer for £10. Worth a go I reasoned

WARNING: Only attempt this if you are capable with electrical items and dismantling things in an orderly and careful fashion. If in doubt get a qualified repairer to undertake this

So first of all I removed and disconnected the microwave from its recess and from the electricity.

 I reasoned that working on the door would be much easier with it removed from the oven

 This necessitated removing the case from the oven, which was secured by screws along the back and sides. I placed all screws and removed hardware on a plastic tray so I didn't lose anything

This gave me access to the hinges which each had two bolts holding in place. Accessing the top bolts was easy from above, but the two lower bolts needed access through holes in the base. One of which is blocked by plastic trim which had to also be removed (two more screws)

 Below you see one of the bolts , which conveniently features a Phillips screw head too, via the access hole, the second bolt is blocked by the trim (top)

With the trim removed and the bolts undone (they were very stiff) I was able to remove the entire door

 Here you can see the rust and flaky paintwork

The inside window is surrounded by a plastic surround, which clips into place, and could be removed by gently easing a flat metal tool around the edge to disengage the internal clips. Gently does it,  and it came out without breaking anything .

Removing the plastic surround trim gave access to the window surround . I set about scraping off the loose paintwork using a knife

I reasoned that if the integrity of the door frame was sound i.e. the rust had not caused any structural damage i.e.  holes , it was safe to treat. If the door structure was compromised, then it would not provide a sufficient Microwave screen and would not be safe. I was relieved to find that the rust was surface only , not holes or severe damage to the underlying metal structure.

Once I had the paint scraped back I used a hobby drill with a wire brush attachment to remove as much rust as I could. 

NOTE TAKE GREAT CARE NOT TO SCRATCH THE WINDOW. IT FEATURES A PROTECTIVE METAL MESH WHICH PROTECTS THE EXTERIOR FROM THE MICROWAVE RADIATION.

Once I had the rust sanded back and I'd used a vacuum cleaner to remove the dust, I treated the rusted areas with an anti-rust treatment. It's basically an acid which reacts with the iron oxide and creates a good surface to paint.

 I let this dry, it changes the rust frst to a blue colour then to black.


Once dried over night, I painted the rusted section, with two coats of the  Microwave paint, each coat allowing 24 hours to dry

Here you can see completely reassembled, reversing the sequence above and back to normal.
A repaired rusted door . While the paint finish internally is not as smooth as original, it is sound and not visible externally. Good enough and cheaper than a new oven. Job done