It's not blackhat SEO, and it's very common to create separate domains for the means of SEO. You can even use the same IP address (so you don't actually need a new host or new IP) and the benefit is still there. While it does help if the domains are hosted at separate locations, it isn't necessary.

Any of the articles that do belong on your company blog should be on your company blog. Everything else can go on the secondary domains. Just be sure that you develop the domains as you would your flagship website: with quality and attention to detail. Otherwise they serve no purpose other than for your SEO (no value to visitors) and they could be considered as grey/black-hat SEO.

Your secondary domains also become guinea pigs. You can test new services or link building ideas on them, and if they lose their rank, it certainly isn't good but it's not going to hurt your main domain. It's a layer of abstraction that will both protect your main website's SEO and allow you to start building case studies.

Personally I like to get whoisguard to mask the registrant of the domain, separate them all on different servers, and try to make them as unique as possible. (Tough in a specific industry, though..) I'd recommend you did the same.

Let me know if you have questions about this! Cheers.

I wouldnt consider it "black hat" as long as you're providing valuable, rich content, that is agnostic to your brand.  If you have any other companies in your industry that could also add content, you could really gain some traction and use it as a marketing tool for the industry with some leverage toward your brand.

That being said, there are much more qualified people who could probably clarify issues.. these are just my guestimates.

Now, the same IP address could create an issue.. you may want to host it on another server.

We are currently producing quite alot of engaging content and although it's industry related, it is sometimes quite broad and not always appropriate for our company blog.

The best place for this content is in a folder on your main website such as.... mysite.com/blog/

It is possible to run to installations of wordpress on a single domain.

If you don't want that content on your own site then placing it on a satellite site would be the next choice.

Running two different sites in the same niche is not a sin... and most hosts will give you a second IP address for a very small fee.  Ask them about it.