Alternative joining?

Published:  18 October, 2007

The answer to this month’s trouble shooting teaser is provided by Bob Orme of Henkel, maker of Loctite brand adhesives.

 

Q:

We have been successfully using an anaerobic adhesive for the assembly of threaded parts delivered from a third party supplier for many years. Very recently, we noticed that the adhesive would not cure on the components. Further investigation revealed that the plating procedure on the parts had been changed from Hexvalent Chrome to Trivalent Chrome. Can adhesives still be used on this replacement material – or do we have to find another way of joining the components?

 

A:

A number of customers have faced this same situation because recent changes in Health and Safety rulings mean that Hexvalent chrome is no longer acceptable as a plating method. This switch to Trivalent Chrome can mean that a change of threadlocking adhesive used with these components may be necessary. That’s because the curing rate of anaerobic adhesives varies according to the surfaces involved – and Trivalent Chrome is one of the least effective materials to promote a cure. What is needed here is an anaerobic that has been developed for just such surfaces. In our range, Loctite 2701 was created for use where previously a slow cure would have been experienced. This product is a high strength anaerobic that can be readily used for all metal fasteners (including stainless steels and those with protective coatings such as zinc) where regular removal for maintenance is not required. The customers who have had to make this change of plating and threadlocking compound have had no problems.

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