The cash offer values Exova at 26% more than the average market valuation over the past year.
The combined business would have about 6,200 employees and nearly 200 laboratories and operations in more than 30 countries.
The deal remains subject to approval from Exova shareholders and regulators.
Exova, which is 54%-owned by private equity group CD&R, recently announced that it had been holding talks with several potential bidders, including London-based Element.
Exova provides laboratory-based testing, calibration and related services for sectors such as pharmaceuticals, aerospace, engineering and construction.
Element, which is owned by private equity investor Bridgepoint, offers materials and product testing to the aerospace, oil and gas and transportation sectors.
Element chief executive Charles Noall said: "We are very excited about the potential of combining these two great businesses to better serve our customers and support their growth.
"This transaction will create a truly global product and materials testing business, increasing Element's operational reach across key markets in the US, Europe and Asia.
"The combined UK-headquartered group will benefit from deep pools of technical talent, very significant testing capacity and a strong network of facilities to support our customers' global supply chains.
"We believe that this acquisition will facilitate greater flexibility to invest further in capacity and technology, driving further opportunities across the combined group."
Edinburgh-based testing services firm Exova has accepted a £620m takeover offer by rival Element Materials Technology Group.