Corrosion resistance

Two grades are available:

• Grade 1: internal applications.
• Grade 3: external applications

When choosing a padlock for harsh environments, you can also look at the padlock's IP rating. Read our guide here: https://www.keyprint.co.uk/news/ip68-padlocks-what-are-the-benefits.

Security requirements

Padlocks are graded from 1 (lowest) to 6 (highest). Security requirements under the standard closely follow the CEN grading system for padlocks that ranks security performance from Grade 1 to Grade 6.

The testing puts padlocks through controlled, repeatable abuse to test their resistance to:

• Pulling.
• Twisting.
• Cutting.
• Impact.
• Freezing.
• Drilling.
• Key differentiation and more.

Let’s have a look at the table below:

Practical Advice for Locksmiths

A high-grade padlock on a weak hasp is pointless. You can fit a Grade 5 lock, but if the staple bends or the fixings fail, that’s what gives way first. The lock is only as strong as what it’s attached to.

What’s actually being secured? Where is it located? What’s a realistic method of attack in that setting? Are there any insurance requirements that need to be met? And does key control matter beyond simple convenience?

You don’t need a long checklist on paper, but running through those points mentally tends to catch most issues before they become call-backs. That usually tells you the right grade for that job.

And not every single job needs the highest grade. Balance the risk, the budget, and how it’s being used. The real value is also in explaining that to customers. Most people don’t see the difference between a £15 padlock and a £60 one until you show them, especially in terms of how long each will hold up under attack.

Common Mistakes to Avoid

Ignoring CEN ratings entirely is one of them, and relying on “heavy duty” labels instead of something measurable. Using indoor padlocks outside is another, especially in exposed areas.

Open shackles tend to get specified where they shouldn’t, simply because they’re easier to fit, and key control is often overlooked until it becomes a problem later.

But probably the most common mistake is still pairing a strong padlock with weak fittings. It looks secure, but it doesn’t behave that way when it’s tested.

Conclusion

Standards like BS EN 12320 give you a baseline. They tell you what a padlock can do in controlled conditions.

But in practice, security is never just the padlock. It’s the padlock, the hasp, how it’s fitted, and how it’s used day to day. Get that combination right, and the rating starts to mean something.