I'm TV technician, but I don’t know how to save or protect the boards in my workshop
For long term storage, what I usually do is put the item in an anti-static plastic bag, put some desiccant packets if available, then seal it (video) using an impulse sealer. This method has yet to fail me.
The plastic, desiccant, and impulse sealer can be acquired for cheap, at least in the Philippines.
When comparing environments care must be made with comparisons.
I am in New Zealand. In my city corrosion rates are high. Elsewhere in the country corrosion rates are much lower. While temperatures and rainfall can be similar or different the main factor is distance from the sea (!).
Note: Maracaibo climate is hot all year round (about 25C) and moderately wet in winter. It is on the ocean. Corrosive salt in the air is probably a major problem (as jsotola says). It is NOTHING like Las Vegas which is far from the sea, gets hotter and much colder and is very dry. ie it is always important to look at actual parameters
Storage in an area fed with filtered contamination free and low humidity air can help.
A very low airflow via a suitable filter is OK as long as overall you maintain even a slight "positive pressure" so the outside air is eliminated.
A good quality conformal coating will provide an excellent solution, but car must be taken not to coat connectors and in some cases "wicking" into some sockets and similar can occur.
As an example only, Dowsil 1-2577 is excellent but may not be readily available to you. This is expensive in small volumes, gets MUCH cheaper in moderate amounts and covers a large area - a film 0.1mm thick is adequate and can be applied by dipping brushing or spraying.
A cheap conformal coating which MAY be adequate - if using it you should test it on some target boards in your environment - is "polyurethane spray" / varnish / laquer. This is not as effective as eg 1-2577 but is very low cost and widely available. Polyurethanes usually set by absorbing moisture from the air - it would probably be wise to ensure that the moisture that is absorbed while drying is salt fee. As with any conformal coating, be aware of coating contacts and possible issues with "wicking" on connectors and sockets.
Anticorrosion vapour emitting products have been mentioned. These can work well but have major problems if used with incompatible materials.
i.e., Anti corrosion vapor emitters MAY be suitable BUT always ask the manufacturer - whether re Zerust or similar products.
From the Wikipedia article on Volatile Corrosion Inhibitor:
- " ... Restrictions and limitations in the use of VCI. VCI materials will not protect all metals from corrosion; in fact, they appear to increase the rate of corrosion in certain metals. VCI materials must not be used to protect any assemblies containing optical systems or precision moving parts which have been coated with a preservative or lubricant, unless otherwise specified. Items protected with bonded films, such as molybdenum (a dry lubricant), are not included in this category . VCI materials are affected by heat and light. They lose their effectiveness as the temperature increases and they decompose if exposed to direct sunlight for extended periods. They also decompose in the presence of acids or strong alkalies. Precautions must be taken when VCI is used with items, assemblies, and subassemblies containing zinc plate, cadmium, zinc. base alloys, magnesium base alloys, lead base alloys, and alloys of other metals including solders and brazing alloys. If such items contain more than 30 percent of zinc or 9 percent of lead, they must not be preserved with VCI. In all cases direct contact of VCI with non ferrous metals except aluminum and aluminum-base alloys should be avoided unless specific permission has been granted. Care should also be taken with assemblies containing plastics, painted parts, or components of natural or synthetic rubber. Assemblies containing parts made of these materials should not be packed with VCI until proof is established that they have passed the compatibility test required by Specification Mn..-I-8574. ... "
I think you can stick them in an airtight box with rust inhibiting vapour block.
https://www.zerust.com/products/vci-emitters-diffusers/
Just make sure your box isn't a plastic box ridden with static charge.