Learn Hardcore Turkish: Demir kapıları boyamadan önce pas temizleme işlemleri yapılmalıdır. - Rust removal procedures must be carried out before painting the iron doors.

The suffix -madan is the negative converb form of a verb plus the ablative case (-ma negative + -dan ablative). It literally means “without doing X,” and when followed by önce it gives “before doing X.”
Formation:
• boya (root “paint”)
• + ma (negative gerund) → boyama (“not painting”)
• + dan (ablative) → boyamadan
So boyamadan önce = “before painting.”

Why is kapıları used instead of just kapılar?

kapılar is “doors” (kapı + -lar plural). We add -ı to make it accusative because the doors are a definite, specific object here (“the iron doors”). So:
kapı + lar (plural) → kapılar
kapılar + ı (accusative) → kapıları

Why does demir stay uninflected while kapı takes plural -lar and case -ı?

In Turkish, adjectives (or nouns used as adjectives) do not take number or case endings—only the head noun does. Here demir (“iron”) describes kapı (“door”), so you pluralize and case-mark kapı:
kapı + lar + ı → kapıları, while demir remains unchanged.

What is temizleme in pas temizleme işlemleri, and how is it formed?

temizleme is a deverbal noun (gerund) formed from the verb temizlemek (“to clean”) by adding -me. It functions like an English “-ing” noun:
temizle + me → temizleme = “cleaning”

Why is there an extra -i in işlemleri (“pas temizleme işlemleri”)?

işlemler is the plural of işlem (“process, operation”). The suffix -i on işlemler can be seen as:

The original accusative marker that remains when an object becomes the subject in a passive sentence.
A 3rd-person possessive marker used to signal definiteness (“the processes”).
Either way, işlemleri = “(the) processes.”

What does yapılmalıdır mean, and how is this form built?

yapılmalıdır is the passive necessity form of yapmak (“to do”). It’s built as:
• yap- (root “do”)
• + -ıl (passive) → yapıl- = “be done”
• + -malı (necessity) → yapılmalı = “must be done”
• + -dır (formal copula) → yapılmalıdır = “it must be done.”

Why does the example use boyamadan önce instead of boyanmadan önce?

Both are possible:

boyamadan önce uses the active converb of boyamak (“to paint”) and means “before (someone) paints (it).”
boyanmadan önce uses the passive converb of boyanmak (“to get painted”) and means “before (it) gets painted.”
In instructions they’re largely interchangeable; the active form highlights the action, while the passive highlights the doors receiving paint.

How could you rephrase the sentence in a more active way with yapmalıyız?

You can specify “we” and use the active necessity yapmalıyız (“we must do”):
Pas temizleme işlemlerini demir kapıları boyamadan önce yapmalıyız.
= “We must carry out the rust-cleaning processes before painting the iron doors.”