Online B2I parts marketing ("business to industrial") is challenging versus B2B or B2B online marketing. This is due to several factors:

• Very long sales cycles, often up to 2 years
• High risk of last-minute cancellations due to product spec changes or the final manufacturer (producer) decides to scrap a project at the last minute
• Requirements to meet such as the parts company needing to be ISO compliant or the parts needing to be conflict minerals compliant
• Offering a range of custom versus stock, or even semi-custom, parts options 
• Working with manufacturers who then provide a more assembled part to the primary manufacturer
• Conflict with keywords in the search engines including different names (industry jargon) for the same part
• Attempting to reach product engineers and design firms who sit at their desks in a main office, so there is no geographic specificity other than perhaps by country - such as looking for a "USA manufacturer of XYZ parts"

Started working years ago for one such client in Stamford, CT.  The company manufactures friction hinges, also called torque hinges or positioning hinges as well as a few other names.  Helped them over the years with several ways to reach these coveted prospective mechanical engineers, product engineers, directors of procurement for industrial parts companies, and product design firms. These included:  SEO, YouTube marketing, press releases, Google Ads, LinkedIn optimization and LinkedIn ads, Tiered backlinks, LinkedIn group outreach, design publication outreach, other social media, and image optimization. 

Here is more about the company:

• Hingemanufacturers.org
• Facebook
• Pinterest
• LinkedIn
• YouTube
• GlobalSpec directory
• ThomasNet listing
• CBIA News article
• Infographic